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Gene-Culture Coevolution and Human Diet

March 2010
American Scientist 98(2):140-147

DOI:10.1511/2010.83.140

Authors:

University of Turku

Researchers Olli Arjamaa and Timo Vuorisalo describe the biological and cultural evolution of hominid diets, concluding with three examples of cultural evolution that led to genetic changes in Homo sapiens. The first hominid species arose 10 to 7 million years ago in late Miocene Africa. The change in diet in part was made possible by stone tools used to manipulate food items. The oldest known stone tools date back to 2.6 million years. Progressive changes in diet were associated with changes in body size and anatomy. Increased use of C 4 plants was indeed gradually followed by increased consumption of meat, either scavenged or hunted. Several factors contributed to increased meat availability. First, savanna ecosystems with several modern characteristics started to spread about 1.8 million years ago. A classic example of gene-culture co-evolution is lactase persistence (LP) in human adults.

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Few would argue against the propo-

sition that in the animal kingdom

adaptations related to food choice and

foraging behavior have a great impact

on individuals’ survival and reproduc-

tion—and, ultimately, on their evolu-

tionary success. In our own species,

however, we are more inclined to view

food choice as a cultural trait not direct-

ly related to our biological background.

This is probably true for variations in

human diets on small scales, manifested

both geographically and among ethnic

groups. Some things really are a matter

of taste rather than survival.

On the other hand, some basic

patterns of our nutrition clearly are

evolved characters, based on between-

generation changes in gene frequen-

cies. As Charles Darwin cautiously

forecast in the last chapter of On the

Origin of Species, his theory of natural

selection has indeed shed “some light”

on the evolution of humans, includ-

ing the evolution of human diet. The

long transition from archaic hunter-

gatherers to post-industrial societies

has included major changes in forag-

ing behavior and human diet.

The traditional view holds that our

ancestors gradually evolved from

South and East African fruit-eaters to

scavengers or meat-eaters by means of

purely biological adaptation to chang-

ing environmental conditions. Since

the 1970s, however, it has become in-

creasingly clear that this picture is too

simple. In fact, biological and cultural

evolution are not separate phenomena,

but instead interact with each other

in a complicated manner. As Richard

Dawkins put it in The Selfish Gene,

what is unusual about our species can

be summed up in one word: culture.

A branch of theoretical population

genetics called gene-culture coevolu-

tionary theory studies the evolution-

ary phenomena that arise from the

interactions between genetic and cul-

tural transmission systems. Some part

of this work relies on the sociobiologi-

cally based theoretical work of Charles

J. Lumsden and E. O. Wilson, sum-

marized in Genes, Mind, and Culture.

Another branch of research focuses on

the quantitative study of gene-culture

coevolution, originated among others

by L. L. Cavalli-Sforza and M. W. Feld-

man. Mathematical models of gene-

culture coevolution have shown that

cultural transmission can indeed mod-

ify selection pressures, and culture can

even create new evolutionary mecha-

nisms, some of them related to human

cooperation. Sometimes culture may

generate very strong selection pres-

sures, partly due to its homogenizing

influence on human behavior.

A gene-culture coevolutionary per-

spective helps us to understand the

process in which culture is shaped by

biological imperatives while biological

properties are simultaneously altered

by genetic evolution in response to

cultural history. Fascinating examples

of such gene-culture coevolution can

be found in the evolution of human

diet. Richard Wrangham’s recent book,

Catching Fire: How Cooking Made Us

Human, focused on impacts of taming

fire and its consequences on the qual-

ity of our food. Some scholars favor

a memetic approach to this and other

steps in the evolution of human diet.

Memetics studies the rate of spread

of the units of cultural information

called memes. This term was coined by

Dawkins as an analogy to the more fa-

miliar concept of the gene. A meme can

be, for instance, a particular method of

making fire that makes its users better

adapted to utilize certain food sources.

As a rule, such a meme spreads in the

population if it is advantageous to its

carriers. Memes are transmitted be-

tween individuals by social learning,

which, as we all know, has certainly

been (and still is) very important in the

evolution of human diet.

In the following paragraphs, we will

review the biological and cultural evo-

lution of hominid diets, concluding

with three examples of cultural evo-

lution that led to genetic changes in

Homo sapiens.

The First Steps in the Savanna

The first hominid species arose 10 to 7

million years ago in late Miocene Afri-

ca. In particular, Sahelanthropus tchaden-

sis, so far the oldest described homi-

nid, has been dated to between 7.2 and

6.8 million years. Hominids probably

evolved from an ape-like tree-climbing

ancestor, whose descendants gradually

became terrestrial bipeds with a sub-

stantially enlarged brain. The overall

picture of human evolution has chan-

ged rather dramatically in recent years,

and several alternative family trees for

human origins have been proposed.

The major ecological setting for

human evolution was the gradually

drying climate of late-Miocene and

Pliocene Africa. Early hominids re-

Gene-Culture Coevolution and Human Diet

Rather than acting in isolation, biology and culture have interacted

to develop the diet we have today

Olli Arjamaa and Timo Vuorisalo

Olli Arjamaa received his Ph.D. in animal

physiology at the University of Turku in 1983,

and his M.D. at the University of Oulu in 1989

(both in Finland). He is adjunct professor at the

Center of Excellence of Evolutionary Genetics

and Physiology, Department of Biology, Univer-

sity of Turku. His main research interest is the

evolutionary physiology of natriuretic peptides.

Timo Vuorisalo received his Ph.D. in ecological

zoology at the University of Turku in 1989. In

1989–1990 he was a visiting postdoctoral fellow

at the Indiana University, Bloomington. He is

senior lecturer of Environmental Science and

adjunct professor in the Department of Biology,

University of Turku. His research interests in-

clude evolutionary ecology, environmental his-

tory and urban ecology. Address: Department of

Biology, 20014 Turun yliopisto, Finland. Email:

olli.arjamaa@utu.fi

with permission only. Contact perms@amsci.org.

Figure 1. Genetic and cultural evolution are often thought of as operating independently of each other’s influence. Recent investigations, how-

ever, show that this is far too simple a picture. Cultural preferences for certain foods, for example, may favor genetic changes that help people

utilize them. One example is the practice of animal husbandry for milk production, which can cause the frequency of lactose tolerance—the

ability to process this milk sugar as an adult—to vary geographically even within continents. Although only about 3 percent of people in Thai-

land (top) have lactose tolerance, the proportion in northern India, where dairy activity is common (above), is about 70 percent.

Donald Nausbaum/CorbisJeremy Homer/Corbis

with permission only. Contact perms@amsci.org.

sponded to the change with a com-

bination of biological and cultural

adaptations that together enhanced

their survival and reproduction in the

changing environment. This adaptive

complex probably included increas-

ingly sophisticated bipedality, com-

plex social behavior, making of tools,

increased body size and a gradual

change in diet. In part, the change in

diet was made possible by stone tools

used to manipulate food items. The

oldest known stone tools date back to

2.6 million years. Stone tool technolo-

gies were certainly maintained and

spread by social learning, and very

likely the same was true for changes in

foraging tactics and choice of food.

The main data sources on homi-

nid paleodiets are fossil hominid

remains and archaeological sites.

Well-preserved fossils allow detailed

analyses on dental morphology and

microwear, as well as the use of paleo-

dietary techniques that include stable

isotope analysis of bone and dentine

collagen, as well as enamel apatite.

Other useful and widely applied meth-

ods include comparisons of fossils

with extant species with known den-

tal morphology and diets. The main

problem with dental morphology and

wear analyses is that they indicate the

predominant type of diet rather than

its diversity. Thus, it is always useful

to combine paleodietary information

from many sources. Archaeological

sites may provide valuable informa-

tion on refuse fauna, tools and home-

range areas of hominids, all of which

have implications for diet.

Much recent attention has been

focused on stable isotope analysis of

bone and collagen. These techniques

allow comparisons of animals con-

suming different types of plant diets.

This is important, as plant remains

seldom fossilize, so the proportion

of animals in the diets of early homi-

nids is easily exaggerated. In stable

isotope analysis it may be possible to

distinguish between diets based on C3

plants and those based predominantly

on C4 plants. C3 and C4 are two differ-

ent biochemical pathways for carbon

fixation in photosynthesis. Plants that

utilize the C3 photosynthetic pathway

discriminate against 13C, and as a re-

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Figure 2. Major events in hominid evolution can be viewed from a gene-culture coevolution perspective. (Note the logarithmic scales at both ends

of the time line, brown dashes.) Contrary to popular belief, bipedality did not evolve to free hands for manufacturing and use of tools (an example

of old teleological thinking not accepted by scientists). In fact, upright posture preceded tool-making by at least 2 million years. Indeed, Ardi, the

celebrated and well-preserved specimen of Ardipithicus ramidus, seems to have moved upright already 4.4 million years ago, and the same may

have been true for the much older Sahelanthropus tchadensis. Bipedality, increasingly complex social behavior, tool-making, increased body size

and dietary changes formed an adaptive complex that enhanced survival and reproduction in the changing African environment. Controlled use

of fire had a great impact on the diet of our ancestors and helped colonization of all main continents by our species. More recently, the dietary

shifts following the Neolithic Revolution provide fascinating examples of the interplay of cultural change and biological evolution.

Figure 3. The use of stone tools contributed

to the dietary change in our ancestors. Sharp-

edged stone tools could slice through the

hides of hunted or scavenged animals, thus

allowing access to meat. Skulls and bones

could be smashed by stone tools, which pro-

vided access to nutritious tissues such as

bone marrow or brain.

Museum of Anthropology, University of Missouri

with permission only. Contact perms@amsci.org.

sult C3 plants have clearly depleted

13C/12C ratios. In contrast, plants that

utilize the C4 photosynthetic pathway

discriminate less against 13C and are,

therefore, in relative terms, enriched in

13C. C4 plants are physiologically bet-

ter adapted to conditions of drought

and high temperatures, as well as ni-

trogen limitation, than are C3 plants.

Thus it is very likely that the drying

climate of Africa increased the abun-

dance and diversity of C4 plants in

relation to C3 plants.

The traditional view on early homi-

nids separated them into australopith-

ecines that were considered predomi-

nantly fruit eaters, and species of the

genus Homo—that is, H. habilis and H.

erectus—who were either scavengers

or hunters. This traditional separation

has been challenged by paleodietary

techniques that have highlighted the

importance of changes in the makeup

of plant diet outlined above. While the

ancestral apes apparently continued

to exploit the C3 plants abundant in

forest environments, the australopith-

ecines broadened their diet to include

C4 foods, which together with bipedal-

ism allowed them to colonize the in-

creasingly open and seasonal African

environment.

This emerging difference in diet

very likely contributed to the ecologi-

cal diversification between apes and

hominids, and was an important step

in human evolution. The C4 plants for-

aged by australopithecines may have

included grasses and sedges, although

the topic is rather controversial. In-

terestingly, the use of animals as food

sources may also result in a C4-type

isotopic signature, if the prey animals

have consumed C4 plants. Many re-

searchers believe that a considerable

proportion of the diet of australopith-

ecines and early Homo consisted of ar-

thropods (perhaps largely termites),

bird eggs, lizards, rodents and young

antelope, especially in the dry season.

Brain Size, Food and Fire

Progressive changes in diet were as-

sociated with changes in body size

and anatomy. As Robert Foley at the

University of Cambridge has pointed

out, increased body size may broaden

the dietary niche by increasing home-

range area (thus providing a higher

diversity of possible food sources)

and enhanced tolerance of low-quality

foods. A large mammal can afford to

subsist off lower-quality foods than a

small mammal. Moreover, increased

body size enhances mobility and heat

retention, and may thus promote the

ability to adapt to cooler climates. All

these possibilities were realized in the

hominid lineage.

In particular, the origin of H. erectus

about 1.8 million years ago appears

to have been a major adaptive shift in

human evolution. H. erectus was larger

than its predecessors and was appar-

ently the first hominid species to mi-

grate out of Africa. It also showed a

higher level of encephalization (skull

size relative to body size) than seen in

any living nonhuman primate species

today. Increased brain size, in turn, was

associated with a change in diet. The

increase in brain size probably started

about 2.5 million years ago, with grad-

ual transition from Australopithecus to

Homo. Because of the proportionately

high energy requirements of brain

tissue, the evolution of large human

brain size has had important implica-

tions for the nutritional requirements

of the hominid species. According

to the Expensive-Tissue Hypothesis,

proposed in 1995 by Leslie Aiello with

University College London and Peter

Figure 4. Stable carbon isotope analyses show that

early African hominids had a significant C4 com-

ponent in their diet. This may have come either

from eating C4 plant foods or from eating animals

(for example, termites) that consumed C4 plants.

Common C3 plants include (clockwise from top

left) rice and cassava root. A well-known C4 plant

is the giant sedge Cyperus papyrus, which was

used as a food source by ancient Egyptians. Teff

is a common C4 plant in Africa today.

Clockwise: Lucille Reyboz, Ann Johansson, Wolfgang Kaehler, Frans Lanting/Corbis

with permission only. Contact perms@amsci.org.

Wheeler with Liverpool John Moores

University, the high costs of large hu-

man brains are in part supported by

energy- and nutrient-rich diets that in

most cases include meat.

Increased use of C4 plants was in-

deed gradually followed by increased

consumption of meat, either scavenged

or hunted. Several factors contributed

to increased meat availability. First, sa-

vanna ecosystems with several mod-

ern characteristics started to spread

about 1.8 million years ago. This bene-

fited East African ungulates, which in-

creased both in abundance and species

diversity. For top predators such as H.

erectus this offered more hunting and

scavenging possibilities. The diet of H.

erectus appears to have included more

meat than that of australopithecines,

and early Homo. H. erectus probably ac-

quired mammalian carcasses by both

hunting and scavenging. Archaeologi-

cal evidence shows that H. erectus used

stone tools and probably had a rudi-

mentary hunting and gathering econ-

omy. Sharp-edged stone tools were

important as they could slice through

hide and thus allowed access to meat.

These tools also made available tissues

such as bone marrow or brain. Greater

access to animal foods seems to have

provided the increased levels of fatty

acids that were necessary for support-

ing the rapid hominid brain evolution.

As Richard Wrangham has persua-

sively argued, domestication of fire

had a great influence on the diet of

our ancestors. Fire could be used in

cooperative hunting, and to cook meat

and plants. According to hominid fos-

sil records, cooked food may have ap-

peared already as early as 1.9 million

years ago, although reliable evidence

of the controlled use of fire does not

appear in the archaeological record

until after 400,000 years ago. The rou-

tine use of fire probably began around

50,000 to 100,000 years ago. Regular

use of fire had a great impact on the

diet of H. erectus and later species, in-

cluding H. sapiens. For instance, the

cooking of savanna tubers and other

plant foods softens them and increases

their energy and nutrient bioavail-

ability. In their raw form, the starch

in roots and tubers is not absorbed in

the intestine and passes through the

body as nondigestible carbohydrate.

Cooking increases the nutritional qual-

ity of tubers by making more of the

carbohydrate energy available for bio-

logical processes. It also decreases the

risk of microbial infections. Thus, the

use of fire considerably expanded the

range of possible foods for early hu-

mans. Not surprisingly, the spread of

our own species to all main continents

coincides with the beginning of the

routine use of fire.

In relative terms, consumption of

meat seems to have peaked with our

sister species H. neanderthalensis. As

Figure 5. Controlled use of fire was key to changes in hominid diet. Although examples may

date back as far as 400,000 years ago, it probably was not common until roughly 50,000 to

100,000 years ago, as shown in these examples of heat-treated silcrete blade tools from the circa

65,000–60,000-year-old layers at Pinnacle Point Site 5-6(PP5-6) in Africa.

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Figure 6. The carbohydrate revolution began

with the domestication of plants and animals

about 12,000 years ago. Diets prior to the Neo-

lithic differed considerably from what most

people eat today. The contribution of pro-

tein to caloric intake (for example, salmon as

shown in the Finnish spread at right) declined

significantly. In place of the missing protein

came carbohydrates such as potatoes. This

may have driven an increase in the copies of

the human amylase salivary enzyme gene.

Kyle S. Brown, Institute for Human Origins (IHO)

Richard Wareham Fotografie/Alamy

with permission only. Contact perms@amsci.org.

Matt Sponheimer and Julia A. Lee-

Thorp with Rutgers University and

the University of Cape Town have

pointed out, on the basis of extensive

evidence, “there can be little doubt

that Neanderthals consumed large

quantities of animal foods.” Remains

of large to medium-sized mammals

dominate Neanderthal sites. Neander-

thals probably both hunted and for-

aged for mammal carcasses. Perhaps,

unromantically, they had a preference

for small prey animals when hunting.

And in northern areas colonized by

the Neanderthals, there was probably

no competition for frozen carcasses.

The control of fire by the Neanderthals

(and archaic modern humans), how-

ever, allowed them to defrost and use

such carcasses.

The Carbohydrate Revolution

The Neolithic or Agricultural Revolu-

tion, a gradual shift to plant and animal

domestication, started around 12,000

years ago. For our species this cultural

innovation meant, among many other

things, that the proportion of carbohy-

drates in our diet increased consider-

ably. Cereal grains have accounted for

about 35 percent of the energy intake

of hunter-gatherer societies, whereas

it makes up one-half of energy intake

in modern agricultural societies—for

example, in Finnish young adults (see

Figure 6). The Neolithic Revolution

also included domestication of mam-

mals, which in favorable conditions

guaranteed a constant supply of meat

and other sources of animal protein.

Although fire likely played a role in

the early utilization of carbohydrates,

the big shift in diet brought about by

plant domestication has its roots in the

interplay of cultural change and bio-

logical evolution. Sweet-tasting carbo-

hydrates are energy rich and therefore

vital for humans. In the environment

of Paleolithic hunter-gatherer popula-

tions, carbohydrates were scarce, and

therefore it was important to effective-

ly find and taste sweet foods. When

eaten, large polymers such as starch are

partly hydrolyzed by the enzyme amy-

lase in the mouth and further cleaved

into sugars, the sweet taste of which

might have functioned as a signal for

identifying nutritious food sources.

(It is interesting to note that the fruit

fly Drosophila melanogaster perceives

the same compounds as sweet that we

do.) Later, in the Neolithic agriculture,

during which humans shifted to con-

sumption of a starch-rich diet, the role

of the amylase enzyme in the digestive

tract became even more important in

breaking down starch.

Salivary amylase is a relatively re-

cent development that first originated

from a pre-existing pancreatic amylase

gene. A duplication of the ancestral

pancreatic amylase gene developed

salivary specificity independently both

in rodents and in primates, emphasiz-

ing its importance in digestion. Ad-

ditionally, its molecular biology gives

us a new insight into how evolution

has made use of copy number varia-

tions (CNVs, which include deletions,

insertions, duplications and complex

multisite variants) as sources of ge-

netic and phenotypic variation; single-

nucleotide polymorphisms (SNPs)

were once thought to have this role

alone. CNVs may also involve com-

plex gains or losses of homologous

sequences at multiple sites in the

genome, and structural variants can

comprise millions of nucleotides with

heterogeneity ranging from kilobases

to megabases in size.

Analyses of copy number variation

in the human salivary amylase gene

(Amy1) found that the copy number

correlated with the protein level and

that isolated human populations with

a high-starch diet had more copies of

Amy1. Furthermore, the copy number

and diet did not share a common an-

cestry; local diets created a strong posi-

tive selection on the copy number vari-

ation of amylase, and this evolutionary

sweep may have been coincident with

the dietary change during early stages

of agriculture in our species. It is in-

teresting to note that the copy number

variation appears to have increased in

the evolution of human lineage: The

salivary protein levels are about six to

eight times higher in humans than in

chimpanzees and in bonobos, which

are mostly frugivorous and ingest little

starch compared to humans.

Transition to Dairy Foods

A classic example of gene-culture co-

evolution is lactase persistence (LP) in

human adults. Milk contains a sugar

named lactose, which must be digested

by the enzyme lactase before it can be

absorbed in the intestine. The ability to

digest milk as adults (lactose tolerance)

is common in inhabitants of Northern

Europe where ancient populations are

assumed to have used milk products

as an energy source to survive the cold

and dark winters, whereas in southern

Europe and much of Asia, drinking

milk after childhood often results in

gastrointestinal problems. If the intes-

tine is unable to break down lactose to

glucose and galactose—due to lack of

lactase or lactase-phlorizin hydrolase

(LPH) enzyme, normally located in the

villi of enterocytes of the small intes-

tine—bacterial procession of lactose

causes diarrhea, bloating and flatu-

lence that can lead to fatal dehydra-

tion in infants. On the other hand, milk

provides adults with a fluid and rich

source of energy without bacterial con-

tamination, enhancing their survival

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8 &

Figure 7. Albano Beja-Pereira and colleagues

have done geographic matching between milk

gene diversity in cattle, lactose tolerance in

contemporary humans and locations of Neo-

lithic cattle farming sites. The dark orange

color in a shows where the greatest milk

gene uniqueness and allelic diversity occur

in cattle. In b lactase persistence is plotted

in contemporary Europeans. The darker the

color, the higher the frequency of the lactase

persistence allele. The dashed line in b shows

the geographic area in which the early Neo-

lithic cattle pastoralist culture emerged. (Im-

age adapted from Beja-Pereira et al. 2003.)

with permission only. Contact perms@amsci.org.

and fitness. Therefore, in the past the

phenotype of lactase persistence un-

doubtedly increased the relative repro-

ductive success of its carriers.

Recent findings of molecular biology

show that a single-nucleotide polymor-

phism that makes isolated populations

lactase persistent has been “among the

strongest signals of selection yet found

for any gene in the genome.” Lactase

persistence emerged independently

about 10,000 to 6,000 years ago in Eu-

rope and in the Middle East, two areas

with a different history of adaptation

to the utilization of milk. The earliest

historical evidence for the use of cat-

tle as providers of milk comes from

ancient Egypt and Mesopotamia and

dates from the 4th millennium .. Still

today there are large areas of central

Africa and eastern Asia without any

tradition of milking, and many adults

in these countries are physiologically

unable to absorb lactose. The ancient

Romans did not drink milk, and this

is reflected in the physiology of their

Mediterranean descendants today.

The first evidence for a SNP as a

causative factor in LP came from a

group of Finnish families. A haplo-

type analysis of nine extended Finnish

families revealed that a DNA variant

(C/T-13910) located in the enhancer el-

ement upstream of the lactase gene

associated perfectly with lactose intol-

erance and, because it was observed

in distantly related populations, sug-

gested that this variant was very old.

Later it was shown that this allele had

emerged independently in two geo-

graphically restricted populations in

the Urals and in the Caucasus, the first

time between 12,000 and 5,000 years

ago and the second time 3,000 to 1,400

years ago. Yet Saudi Arabian popula-

tions that have a high prevalence of LP

have two different variants introduced

in association with the domestication

of the Arabian camel about 6,000 years

ago. In Africa, a strong selective sweep

in lactase persistence produced three

new SNPs about 7,000 years ago in

Tanzanians, Kenyans and Sudanese,

reflecting convergent evolution during

a similar type of animal domestication

and adult milk consumption.

All these facts indicate that there has

been a strong positive selection pres-

sure in isolated populations at different

times to introduce lactose tolerance,

and this has taken place through sev-

eral independent mutations, implying

adaptation to different types of milk-

ing culture. Lactase persistence was

practically nonexistent in early Euro-

pean farmers, based on the analysis of

Neolithic human skeletons, but when

dairy farming started in the early Neo-

lithic period, the frequency of lactase

persistence alleles rose rapidly under

intense natural selection. The cultural

shift towards dairy farming apparently

drove the rapid evolution of lactose

tolerance, making it one of the strong-

est pieces of evidence for gene-culture

coevolution in modern humans. In

other words, the meme for milking

had local variants, which spread rap-

idly due to the positive effects they

had on their carriers.

We must bear in mind, however, that

the transcription of a gene is under

complex regulation, as is the C/T -13910

variant: It contains an enhancer ele-

ment through which several transcrip-

tion factors probably contribute to the

regulation of the lactase gene in the

intestine. In addition, lactose toler-

ance in humans and the frequencies

of milk protein genes in cattle appear

to have also coevolved. When the geo-

graphical variation in genes encoding

the most important milk proteins in

a number of European cattle breeds

and the prevalence of lactose tolerance

in Europe were studied, the high di-

versity of milk genes correlated geo-

graphically with the lactose tolerance

in modern Europeans and with the

locations of Neolithic cattle farming

sites in Europe (see Figure 7). This cor-

relation suggests that there has been a

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Figure 8. Lactose intolerance in adult human beings is, in fact, the rule rather than the exception, although its prevalence may well be declin-

ing as the single nucleotide polymorphism that causes lactase persistence spreads. Note the wide variation in lactose intolerance over short

geographic distances. Particularly in African cultures, the prevalence of dairy farming is strongly correlated to lactose tolerance. Gray areas

indicate areas where no data are available. (Map adapted from Wikimedia Commons.)

with permission only. Contact perms@amsci.org.

gene-culture coevolution between cat-

tle and human culture leading towards

larger herds with a wider distribution

of gene frequencies, resulting in the

selection of increased milk production

and changed composition of milk pro-

teins more suitable for human nutri-

tion. In the future, we will know even

more about the geographical evolu-

tion of LP, as it has become possible to

rapidly genotype large numbers of in-

dividuals harboring lactose tolerance-

linked polymorphisms producing var-

ious gastrointestinal symptoms after

lactose ingestion.

We Are Still Evolving

As shown above, culture-based chang-

es in diet (which can be called memes)

have repeatedly generated selective

pressures in human biological evo-

lution, demonstrated for instance by

the single nucleotide polymorphism

of lactase persistence and the copy

number variation of amylase. These

selective sweeps took place 10,000

to 6,000 years ago when animal and

plant domestication started, marking

the transition from the Paleolithic to

the Neolithic era. Much earlier, genet-

ic changes were certainly associated

with the dietary changes of australop-

ithecines and H. erectus.

What about the future? Can we, for

instance, see any selection pressure

in the loci of susceptibility to diet-

associated diseases? The answer seems

to be yes. The risk of Type II diabetes

(T2D) has been suggested to be a tar-

get of natural selection in humans as it

has strong impacts on metabolism and

energy production, and therefore on

human survival and fitness. Genome-

wide and hypothesis-free association

studies have revealed a variant of the

transcription factor 7–like (TCF7L2)

gene conferring the risk of T2D. Later,

in Finns, a similar genome-wide T2D

study increased the number of vari-

ants near the TCF7L2 to 10. When re-

fining the effects of TCF7L2 gene vari-

ants on T2D, a new variant of the same

gene that has been selected for in East

Asian, European and West African

populations was identified. Interest-

ingly, this variant suggested an asso-

ciation both with body mass index and

with the concentrations of leptin and

ghrelin, the hunger-satiety hormones

that originated approximately during

the transition from Paleolithic to Neo-

lithic culture. In support of the notion

that selection is an on-going process in

human physiological adaptation, the

analysis of worldwide samples of hu-

man populations showed that the loci

associated with the risk of T2D have

experienced a recent positive selection,

whereas susceptibility to Type I dia-

betes showed little evidence of being

under natural selection.

In the near future, genome-wide

scans for recent positive selections will

increase our understanding of the co-

evolution between the ancient genome

and diet in different populations, pro-

jecting to problems in modern nutrition-

al qualities. As has been suggested here,

that understanding is likely to be con-

siderably more nuanced than the simple

“hunter-gatherer-genes-meet-fast-food”

approach so often put forward.

References

Beja-Pereira, A., G. Luikart, P. R. England et

al. 2003. Gene-culture coevolution between

cattle milk protein genes and human lactase

genes. Nature Genetics 35:311–13.

Bowman, D. M. J. S., J. K. Balch, P. Artaxo et

al. 2009. Fire in the Earth system. Science

324:481–84.

Eaton, S. B. 2006. The ancestral human diet:

What was it and should it be a paradigm

for contemporary nutrition? Proceedings of

the Nutritional Society 65:1–6.

Enattah, N. S., T. G. K. Jensen, M. Nielsen et

al. 2008. Independent introduction of two

lactase-persistence alleles into human pop-

ulations reflects different history of adap-

tation to milk culture. American Journal of

Human Genetics 82:57–72.

Foley, R. 1987. Another Unique Species: Patterns

in Human Evolutionary Ecology. Hong Kong:

Longman Group.

Helgason, A., S. Pálsson, G. Thorleifsson et al.

2007. Refining the impact of TCF7L2 gene

variants on type 2 diabetes and adaptive

evolution. Nature Genetics 39:218–25.

Laland, K. N., J. Odling-Smee and S. Myles.

2010. How culture shaped the human ge-

nome: Bringing genetics and the human

sciences together. Nature Reviews Genetics

11:137–48.

Leonard, W. R., J. J. Snodgrass and M. L. Rob-

ertson. 2007. Effects of brain evolution on

human nutrition and metabolism. Annual

Review of Nutrition 27:311–27.

Perry, G. H., N. J. Dominy, K. G. Claw et al.

2007. Diet and the evolution of human

amylase gene copy number variation. Na-

ture Genetics 39:1188–90.

Pickrell, J. K., G. Coop, J. Novembre et al. 2009.

Signals of recent positive selection in a

worldwide sample of human populations.

Genome Research 19:826–37.

Sponheimer, M., and J. Lee-Thorp. 2007. Ho-

minin paleodiets: the contribution of stable

isotopes. In Handbook of Paleoanthropology,

Vol. I: Principles, Methods and Approaches,

eds. W. Henke and I. Tattersall. Berlin:

Springer, pp. 555–85.

Wrangham, R. 2009. Catching Fire: How Cooking

Made Us Human. New York: Basic Books.

For relevant Web links, consult this

issue of American Scientist Online:

http://www.americanscientist.org/

issues/id.83/past.aspx

A comparison of biological and cultural evolution

Article

Full-text available

Mar 2015
J GENET

Petter Portin

This review begins with a definition of biological evolution and a description of its general principles. This is followed by a presentation of the biological basis of culture, specifically the concept of social selection. Further, conditions for cultural evolution are proposed, including a suggestion for language being the cultural replicator corresponding to the concept of the gene in biological evolution. Principles of cultural evolution are put forward and compared to the principles of biological evolution. Special emphasis is laid on the principle of selection in cultural evolution, including presentation of the concept of cultural fitness. The importance of language as a necessary condition for cultural evolution is stressed. Subsequently, prime differences between biological and cultural evolution are presented, followed by a discussion on interaction of our genome and our culture. The review aims at contributing to the present discussion concerning the modern development of the general theory of evolution, for example by giving a tentative formulation of the necessary and sufficient conditions for cultural evolution, and proposing that human creativity and mind reading or theory of mind are motors specific for it. The paper ends with the notion of the still ongoing coevolution of genes and culture.

Consensus rank orderings of molecular fingerprints illustrate the ‘most genuine’ similarities between marketed drugs and small endogenous human metabolites, but highlight exogenous natural products as the most important ‘natural’ drug transporter substrates

Preprint

Full-text available

Feb 2017

We compare several molecular fingerprint encodings for marketed, small molecule drugs, and assess how their rank order varies with the fingerprint in terms of the Tanimoto similarity to the most similar endogenous human metabolite as taken from Recon2. For the great majority of drugs, the rank order varies very greatly depending on the encoding used, and also somewhat when the Tanimoto similarity (TS) is replaced by the Tversky similarity. However, for a subset of such drugs, amounting to some 10% of the set and a Tanimoto similarity of ~0.8 or greater, the similarity coefficient is relatively robust to the encoding used. This leads to a metric that, while arbitrary, suggests that a Tanimoto similarity of 0.75-0.8 or greater genuinely does imply a considerable structural similarity of two molecules in the drug-endogenite space. Although comparatively few (<10% of) marketed drugs are, in this sense, robustly similar to an endogenite, there is often at least one encoding with which they are genuinely similar (e.g. TS > 0.75). This is referred to as the Take Your Pick Improved Cheminformatic Analytical Likeness or TYPICAL encoding, and on this basis some 66% of drugs are within a TS of 0.75 to an endogenite. We next explicitly recognise that natural evolution will have selected for the ability to transport dietary substances, including plant, animal and microbial ‘secondary’ metabolites, that are of benefit to the host. These should also be explored in terms of their closeness to marketed drugs. We thus compared the TS of marketed drugs with the contents of various databases of natural products. When this is done, we find that some 80% of marketed drugs are within a TS of 0.7 to a natural product, even using just the MACCS encoding. For patterned and TYPICAL encodings, 80% and 98% of drugs are within a TS of 0.8 to (an endogenite or) an exogenous natural product. This implies strongly that it is these exogeneous (dietary and medicinal) natural products that are more to be seen as the ‘natural’ substrates of drug transporters (as is recognised, for instance, for the solute carrier SLC22A4 and ergothioneine). This novel analysis casts an entirely different light on the kinds of natural molecules that are to be seen as most like marketed drugs, and hence potential transporter substrates, and further suggests that a renewed exploitation of natural products as drug scaffolds would be amply rewarded.

Coevolution of Genes and Culture in Man

Chapter

Full-text available

Jan 2019

Petter Portin

Biological and cultural evolution share the necessary conditions for evolution in general, the principles of variation, inheritance and selection that together constitute the sufficient condition for biological evolution. In addition, for cultural evolution, there are several other necessary conditions. Cultural evolution also has characteristics that are not observed in biological evolution. These are consequences of the differences in the mode of transfer of information between biological and cultural evolution (Figure 1), leading to the fact that cultural evolution is far more rapid than biological evolution. Biological and cultural evolution affect each other, thus experiencing continuing coevolution. Changes in the genes have been necessary to adopt complex behavioral traits, such as the ability to speak, and changes in culture, such as diet, have caused changes in gene frequencies. Modern studies on molecular genetics suggest that coevolution of culture and genes is the most important factor in our origin and evolution. Key Concepts • The necessary conditions for biological evolution, adaptive changes of gene frequencies in the populations of organisms, are variation, inheritance and selection. • These three phenomena, which can also be called the postulates of the theory of evolution, together also constitute a sufficient condition for biological evolution. • These general principles apply not only to biological evolution but also to the evolution of societies and culture – a theory which is called general Darwinism. • The necessary conditions for cultural evolution include, in addition to the necessary conditions for biological evolution, several other factors as for example storage, collection and accumulation of information; formation of social groups, work and division of labor between individuals; the subsequent development of society; and spoken language. • These similarities in the conditions for biological and cultural evolution affect the interaction between the genes and culture in a specific way making their coevolution possible. • Indeed, many cases of reciprocal coevolutionary interaction between the genes of human individuals or populations and the culture of the population in question have been observed. • Differences in gene frequencies between populations and changes in the genes of individuals have led to differences in the culture of the population in question, and vice versa, thus indicating coevolution between genes and culture.

Consensus rank orderings of molecular fingerprints illustrate the most genuine similarities between marketed drugs and small endogenous human metabolites, but highlight exogenous natural products as the most important ‘natural’ drug transporter substrates

Article

Full-text available

Jun 2017

p class="ADMETabstracttext">We compare several molecular fingerprint encodings for marketed, small molecule drugs, and assess how their rank order varies with the fingerprint in terms of the Tanimoto similarity to the most similar endogenous human metabolite as taken from Recon2. For the great majority of drugs, the rank order varies very greatly depending on the encoding used, and also somewhat when the Tanimoto similarity (TS) is replaced by the Tversky similarity. However, for a subset of such drugs, amounting to some 10 % of the set and a Tanimoto similarity of ~0.8 or greater, the similarity coefficient is relatively robust to the encoding used. This leads to a metric that, while arbitrary, suggests that a Tanimoto similarity of 0.75-0.8 or greater genuinely does imply a considerable structural similarity of two molecules in the drug-endogenite space. Although comparatively few (<10 % of) marketed drugs are, in this sense, robustly similar to an endogenite, there is often at least one encoding with which they are genuinely similar (e.g. TS > 0.75). This is referred to as the Take Your Pick Improved Cheminformatic Analytical Likeness or TYPICAL encoding, and on this basis some 66 % of drugs are within a TS of 0.75 to an endogenite. We next explicitly recognise that natural evolution will have selected for the ability to transport dietary substances, including plant, animal and microbial ‘secondary’ metabolites, that are of benefit to the host. These should also be explored in terms of their closeness to marketed drugs. We thus compared the TS of marketed drugs with the contents of various databases of natural products. When this is done, we find that some 80 % of marketed drugs are within a TS of 0.7 to a natural product, even using just the MACCS encoding. For patterned and TYPICAL encodings, 80 % and 98 % of drugs are within a TS of 0.8 to (an endogenite or) an exogenous natural product. This implies strongly that it is these exogeneous (dietary and medicinal) natural products that are more to be seen as the ‘natural’ substrates of drug transporters (as is recognised, for instance, for the solute carrier SLC22A4 and ergothioneine). This novel analysis casts an entirely different light on the kinds of natural molecules that are to be seen as most like marketed drugs, and hence potential transporter substrates, and further suggests that a renewed exploitation of natural products as drug scaffolds would be amply rewarded. </em

Effect of four different nutrition regimes on the alpha-amylase gene expression in the Indian moth, Plodia interpunctella

Article

Full-text available

May 2016
ANN SOC ENTOMOL FR

Plodia interpunctella (Hübner 1813) (Lepidoptera: Pyralidae) is a cosmopolitan species known to infest a wide range of dried plant materials, including legumes and cereals. In this study, enzyme activity and expression of alpha-amylase gene in larval P. interpunctella grown on four different nutrition regimes was studied. The different nutrition regimes caused differential change in expression of alpha-amylase gene. Compared with the control (artificial diet), the walnut regime caused a 10.8% increase in expression of the alpha-amylase gene, whereas 79.3, 52.5, and 7.5% decreases were observed in the larvae grown on dates, raisins and oleaster respectively. The results also showed that glucose repression varied among larvae feeding on different food diets. The results revealed that expression of the alpha-amylase coding gene was significantly reduced in the larvae grown on date and raisin containing high amounts of glucose. A biochemical assay indicated overlapping of alpha-amylase activity and expression. Complexity in expression of amylase genes suggests the existence of a negative feedback mechanism in the insect larvae. Different parameters can affect gene expression and activation, which may explain the results presented here.

Lactase non-persistence and general patterns of dairy intake in indigenous and mestizo Chilean populations (accepted)

Article

Full-text available

Sep 2015

Lactase persistence (LP) is a genetic trait that has been extensively studied among different countries and ethnic groups. In Latin America, the frequencies of this trait have shown to vary according to the degree of admixture of the populations. Objectives: The objective of this article is to better understand the relationship between this genetic trait and food habits of dairy intake in a multicultural and multiethnic context through analyzing a synthesis of independent studies conducted in four regions of Chile. Methods: Genotypes frequencies for the SNP LCT-13910C>T (rs4988235) and frequency of dairy consumption were obtained from four populations: Polynesians from Easter Island (Rapanui); Amerindians (Mapuche), and Mestizos from the Araucanía region; urban Mestizos from Santiago; and rural Mestizos from the Coquimbo region. The gene frequencies at this locus were compared using the FST index and association between milk consumption and genotype frequencies were estimated. Results: Gene frequency differences for the SNP LCT-13910C>T between Native and Mestizo populations were statistically significant; the LP frequency on Mapuche and Rapanui was 10% and 25%, respectively, whereas in the Mestizo samples, LP frequency was near 40%. Dairy intake was below the standard nutritional recommendations for the four groups studied, but extremely lower among the indigenous populations. A statistically significant association between milk intake and LP phenotype was found among the Santiago and Rapanui populations.

Sosyal Bilimlerde Matematiksel Modellerin Limitleri

Chapter

Sep 2022

Ozgur Aydogmus

1. Giriş Davranış bilimleri arasında yer alan ekonomi, biyoloji, antro-poloji, sosyoloji, psikoloji ve siyaset bilimi vb. disiplinlerin her biri, insan davranışlarını farklı modeller yardımıyla anlamaya çalışır ve bunu davranışların görece farklı yönlerini açıklamak için yaparlar. Bu nedenle kullanılan modellerin farklılık göstermeleri normal kar-şılanmakla birlikte Gintis' e (2022) göre bu modellerin birbirleriyle uyumsuz olması önemli bir sorun teşkil etmektedir. Gintis (2022) bu uyumsuzluğu, birkaç farklı disiplinin kültür ve kültür aktarımı için kullandığı varsayımlarla örneklendirir. Biyolog-lar kültürün en genel anlamıyla bilgiye (yararlı teknikler, üretim için gerekli olan uygulamalar, çocuk yetiştirme yöntemleri, gelenekler vb.) karşılık geldiğini varsaymaktadır. Dolayısıyla, bu disiplin çerçe-vesinde kültürel iletim, bilgi aktarımı olarak görülebilir. Sosyologlar içinse kültür bir dizi ahlaki değerin (adalet, karşılıklılık, güvenilirlik, sadakat, yardımseverlik, nezaket vb.) sosyalleşme vasıtasıyla nesil-den nesile iletilmesi anlamına gelir. Bu disiplinin sınırları içerisinde ahlaki değerler yani kültür bir toplumdan diğerine çok değişmeyen normlar olarak ele alınırken, bir başka disiplin olan antropolojide toplumlar arasındaki kültürel farklılıklar temel inceleme alanların-dan birisi olarak karşımıza çıkar. Sosyologlar, neredeyse bütün top-lumlarda homojen olduğunu varsaydıkları ahlaki normların yani

Darwinian applications to nutrition: The value of evolutionary insights to teachers and students

Article

Jun 2022

Eirik Garnås

Evolutionary biology informs us that the living world is a product of evolution, guided by the Darwinian mechanism of natural selection. This recognition has been fruitfully employed to a number of issues in health and nutrition sciences; however, it has not been incorporated into education. Nutrition and dietetics students generally learn very little or nothing on the subject of evolution, despite the fact that evolution is the process by which our genetically determined physiological traits and needs were shaped. In the present paper, three examples of topics (inflammatory diseases, nutrition transition, and food intolerance) that can benefit from evolutionary information and reasoning are given, with relevant lines of research and inquiry provided throughout. It is argued that the application of evolutionary science to these and other areas of nutrition education can facilitate a deeper and more coherent teaching and learning experience. By recognizing and reframing nutrition as an aspect and discipline of biology, grounded in the fundamental principle of adaptation, revelatory light is shed on physiological states and responses, contentious and unresolved issues, genomic-, epigenomic-, and microbiomic features, and optimal nutrient status and intakes.

Comparative Digestive Physiology

Article

Apr 2013

In vertebrates and invertebrates, morphological and functional features of gastrointestinal (GI) tracts generally reflect food chemistry, such as content of carbohydrates, proteins, fats, and material(s) refractory to rapid digestion (e.g., cellulose). The expression of digestive enzymes and nutrient transporters approximately matches the dietary load of their respective substrates, with relatively modest excess capacity. Mechanisms explaining differences in hydrolase activity between populations and species include gene copy number variations and single-nucleotide polymorphisms. Transcriptional and posttranscriptional adjustments mediate phenotypic changes in the expression of hydrolases and transporters in response to dietary signals. Many species respond to higher food intake by flexibly increasing digestive compartment size. Fermentative processes by symbiotic microorganisms are important for cellulose degradation but are relatively slow, so animals that rely on those processes typically possess special enlarged compartment(s) to maintain a microbiota and other GI structures that slow digesta flow. The taxon richness of the gut microbiota, usually identified by 16S rRNA gene sequencing, is typically an order of magnitude greater in vertebrates than invertebrates, and the interspecific variation in microbial composition is strongly influenced by diet. Many of the nutrient transporters are orthologous across different animal phyla, though functional details may vary (e.g., glucose and amino acid transport with K(+) rather than Na(+) as a counter ion). Paracellular absorption is important in many birds. Natural toxins are ubiquitous in foods and may influence key features such as digesta transit, enzymatic breakdown, microbial fermentation, and absorption. © 2013 American Physiological Society. Compr Physiol 3:741-483, 2013.

Amylase gene expression patterns in Helicoverpa armigera upon feeding on a range of host plants

Article

Apr 2012

Expression of two amylase genes (HaAmy1 and HaAmy2) was studied in Helicoverpa armigera (Hübner; Lepidoptera: Noctuidae) feeding on different host plants and during larval development. Alignment of HaAmy1 and HaAmy2 with other insect amylases shows similarities with known Lepidopteran amylase transcripts. H. armigera amylase gene expression is influenced by the availability of reducing sugars, sucrose and starch content of host plants and further correlates to the pool of reducing sugars in the gut and haemolymph of larvae. HaAmy1 and HaAmy2 during larval development on two host plants viz., maize (cereal) and marigold (ornamental) showed their relative difference. Results support the view that when host plants differ in their macronutrients, relationships of enzymes and substrates are flexible. The present work highlights the distribution of HaAmy1 and HaAmy2 (i) during various stages of insect development (second, fourth and sixth instar, pupa, adult and egg), (ii) in various tissues viz., head, haemolymph, fat body, integument and whole larval body of H. armigera feeding on artificial diet and (iii) in three gut regions of larvae fed on various diets. Complexity in expression of amylase genes suggests existence of mechanisms involved to detect nutrient balance required for avoiding fitness costs and focus their importance in insect nutrition.

How Culture Shaped the Human Genome: Bringing Genetics and the Human Sciences Together

Article

Full-text available

Feb 2010
NAT REV GENET

Researchers from diverse backgrounds are converging on the view that human evolution has been shaped by gene-culture interactions. Theoretical biologists have used population genetic models to demonstrate that cultural processes can have a profound effect on human evolution, and anthropologists are investigating cultural practices that modify current selection. These findings are supported by recent analyses of human genetic variation, which reveal that hundreds of genes have been subject to recent positive selection, often in response to human activities. Here, we collate these data, highlighting the considerable potential for cross-disciplinary exchange to provide novel insights into how culture has shaped the human genome.

Fire in the Earth System

Article

Full-text available

May 2009
SCIENCE

Fire is a worldwide phenomenon that appears in the geological record soon after the appearance of terrestrial plants. Fire influences global ecosystem patterns and processes, including vegetation distribution and structure, the carbon cycle, and climate. Although humans and fire have always coexisted, our capacity to manage fire remains imperfect and may become more difficult in the future as climate change alters fire regimes. This risk is difficult to assess, however, because fires are still poorly represented in global models. Here, we discuss some of the most important issues involved in developing a better understanding of the role of fire in the Earth system.

Signals of recent positive selection in a worldwide sample of human populations

Article

Full-text available

Apr 2009
GENOME RES

Genome-wide scans for recent positive selection in humans have yielded insight into the mechanisms underlying the extensive phenotypic diversity in our species, but have focused on a limited number of populations. Here, we present an analysis of recent selection in a global sample of 53 populations, using genotype data from the Human Genome Diversity-CEPH Panel. We refine the geographic distributions of known selective sweeps, and find extensive overlap between these distributions for populations in the same continental region but limited overlap between populations outside these groupings. We present several examples of previously unrecognized candidate targets of selection, including signals at a number of genes in the NRG-ERBB4 developmental pathway in non-African populations. Analysis of recently identified genes involved in complex diseases suggests that there has been selection on loci involved in susceptibility to type II diabetes. Finally, we search for local adaptation between geographically close populations, and highlight several examples.

Gene-culture coevolution between cattle milk protein genes and human lactase genes

Article

Full-text available

Dec 2003

Milk from domestic cows has been a valuable food source for over 8,000 years, especially in lactose-tolerant human societies that exploit dairy breeds. We studied geographic patterns of variation in genes encoding the six most important milk proteins in 70 native European cattle breeds. We found substantial geographic coincidence between high diversity in cattle milk genes, locations of the European Neolithic cattle farming sites (>5,000 years ago) and present-day lactose tolerance in Europeans. This suggests a gene-culture coevolution between cattle and humans.

The ancestral human diet: What was it and should it be a paradigm for contemporary nutrition?

Article

Full-text available

Feb 2006

Stanley Boyd Eaton

Awareness of the ancestral human diet might advance traditional nutrition science. The human genome has hardly changed since the emergence of behaviourally-modern humans in East Africa 100-50 x 10(3) years ago; genetically, man remains adapted for the foods consumed then. The best available estimates suggest that those ancestors obtained about 35% of their dietary energy from fats, 35% from carbohydrates and 30% from protein. Saturated fats contributed approximately 7.5% total energy and harmful trans-fatty acids contributed negligible amounts. Polyunsaturated fat intake was high, with n-6:n-3 approaching 2:1 (v. 10:1 today). Cholesterol consumption was substantial, perhaps 480 mg/d. Carbohydrate came from uncultivated fruits and vegetables, approximately 50% energy intake as compared with the present level of 16% energy intake for Americans. High fruit and vegetable intake and minimal grain and dairy consumption made ancestral diets base-yielding, unlike today's acid-producing pattern. Honey comprised 2-3% energy intake as compared with the 15% added sugars contribute currently. Fibre consumption was high, perhaps 100 g/d, but phytate content was minimal. Vitamin, mineral and (probably) phytochemical intake was typically 1.5 to eight times that of today except for that of Na, generally <1000 mg/d, i.e. much less than that of K. The field of nutrition science suffers from the absence of a unifying hypothesis on which to build a dietary strategy for prevention; there is no Kuhnian paradigm, which some researchers believe to be a prerequisite for progress in any scientific discipline. An understanding of human evolutionary experience and its relevance to contemporary nutritional requirements may address this critical deficiency.

Refining the impact of TCF7L2 gene variants on type 2 diabetes and adaptive evolution

Article

Full-text available

Mar 2007

We recently described an association between risk of type 2diabetes and variants in the transcription factor 7-like 2 gene (TCF7L2; formerly TCF4), with a population attributable risk (PAR) of 17%-28% in three populations of European ancestry. Here, we refine the definition of the TCF7L2 type 2diabetes risk variant, HapB(T2D), to the ancestral T allele of a SNP, rs7903146, through replication in West African and Danish type 2 diabetes case-control studies and an expanded Icelandic study. We also identify another variant of the same gene, HapA, that shows evidence of positive selection in East Asian, European and West African populations. Notably, HapA shows a suggestive association with body mass index and altered concentrations of the hunger-satiety hormones ghrelin and leptin in males, indicating that the selective advantage of HapA may have been mediated through effects on energy metabolism.

Diet and the evolution of human amylase gene copy number variation

Article

Full-text available

Nov 2007
Nat Genet

Starch consumption is a prominent characteristic of agricultural societies and hunter-gatherers in arid environments. In contrast, rainforest and circum-arctic hunter-gatherers and some pastoralists consume much less starch. This behavioral variation raises the possibility that different selective pressures have acted on amylase, the enzyme responsible for starch hydrolysis. We found that copy number of the salivary amylase gene (AMY1) is correlated positively with salivary amylase protein level and that individuals from populations with high-starch diets have, on average, more AMY1 copies than those with traditionally low-starch diets. Comparisons with other loci in a subset of these populations suggest that the extent of AMY1 copy number differentiation is highly unusual. This example of positive selection on a copy number-variable gene is, to our knowledge, one of the first discovered in the human genome. Higher AMY1 copy numbers and protein levels probably improve the digestion of starchy foods and may buffer against the fitness-reducing effects of intestinal disease.

18 Hominin Paleodiets: The Contribution of Stable Isotopes

Article

Jan 2007

Stable isotope ratio analysis is now regularly used to investigate early hominin diets based on the principle that “you are what you eat.” Analysis of collagen from Neanderthals and anatomically modern humans prior to 20 ka has shown them to be significantly enriched in 15N compared to contemporaneous carnivores and herbivores. This suggests that animal foods were a dominant component of their diets, although it must be borne in mind that collagen δ15N can underemphasize the importance of plant foods. Carbon isotope analysis of the enamel mineral of South African australopiths and early Homo has revealed that these taxa consumed ∼30% C4 foods such as tropical grasses, sedges, or animals that ate these foods. Moreover, the australopiths are characterized by remarkably variable δ13C values. Chimpanzees, in contrast, are nearly pure C3 consumers even in environments with abundant C4 vegetation. These data suggest that when confronted with increasingly open areas, chimpanzees continue to exploit the foods that are most abundant in forest environments, whereas australopiths utilized novel C4 resources in addition to forest foods.

Another Unique Species: Patterns in Human Evolutionary Ecology

Article

Oct 1988
BIOSCIENCE

Effects of Brain Evolution on Human Nutrition and Metabolism

Article

Feb 2007

The evolution of large human brain size has had important implications for the nutritional biology of our species. Large brains are energetically expensive, and humans expend a larger proportion of their energy budget on brain metabolism than other primates. The high costs of large human brains are supported, in part, by our energy- and nutrient-rich diets. Among primates, relative brain size is positively correlated with dietary quality, and humans fall at the positive end of this relationship. Consistent with an adaptation to a high-quality diet, humans have relatively small gastrointestinal tracts. In addition, humans are relatively "undermuscled" and "over fat" compared with other primates, features that help to offset the high energy demands of our brains. Paleontological evidence indicates that rapid brain evolution occurred with the emergence of Homo erectus 1.8 million years ago and was associated with important changes in diet, body size, and foraging behavior.

Gene-Culture Coevolution and Human Diet

Abstract

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