Daniel E Lieberman

Harvard University | Harvard · Department of Human Evolutionary Biology

Over the course of the physical activity transition, machines have largely replaced skeletal muscle as the source of work for locomotion and other forms of occupational physical activity in industrial environments. To better characterize this transition and its effect on back muscles and the spine, we tested to what extent typical occupational acti...

Shoes affect the evolved biomechanics of the foot, potentially affecting running kinematics and kinetics that can in turn influence injury and performance. An important feature of conventional running shoes is heel height, whose effects on foot and ankle biomechanics remain understudied. Here, we investigate the effects of 6–26 mm increases in heel...

During vigorous physical activity, contracting muscles secrete a variety of immunomodulatory and metabolic factors called myokines that perform a variety of functions. Foremost among these is interleukin 6 (IL‐6), which increases fatty acid mobilization and stimulates anti‐inflammatory cytokine release. Despite being well characterized in vigorous...

Running injuries are prevalent, but their exact mechanisms remain unknown largely due to limited real-world biomechanical analysis. Reducing overstriding, the horizontal distance that the foot lands ahead of the body, may be relevant to reducing injury risk. Here, we leverage the geometric relationship between overstriding and lower extremity sagit...

Optical motion capture (OMC) is considered the best available method for measuring spine kinematics, yet inertial measurement units (IMU) have the potential to collect data outside the laboratory. When combined with musculoskeletal modeling, IMU technology may be used to estimate spinal loads in real-world settings. To date, IMUs have not been vali...

Human evolution is defined by a multifaceted interplay of biological and cultural factors, which comprise the focus of a diverse spectrum of scientific fields. This edited volume aims to establish interdisciplinary links through a series of nine studies that critically discuss the current methods, hypotheses frameworks, and future perspectives for...

Noncommunicable diseases (NCDs) are on the rise worldwide. Obesity, cardiovascular disease, and type 2 diabetes are among a long list of “lifestyle” diseases that were rare throughout human history but are now common. The evolutionary mismatch hypothesis posits that humans evolved in environments that radically differ from those we currently experi...

Background: Although human diets varied considerably before agriculture's spread, public perceptions of pre-agricultural diets have been strongly influenced by the Paleo Diet, which prescribes percentage calorie ranges of 19-35% protein, 22-40% carbohydrate, and 28-47% fat, and prohibits foods with added sugar, dairy, grains, most starchy tubers,...

Objectives: We aim to test three questions regarding human eccrine sweat gland density, which is highly derived yet poorly understood. First, is variation in functional eccrine gland density ("FED") explained by childhood climate, suggesting phenotypic plasticity? Second, is variation in FED explained by genetic similarity (a proxy for "geographic...

Globally, we are witnessing the rise of complex, non-communicable diseases (NCDs) related to changes in our daily environments. Obesity, asthma, cardiovascular disease, and type 2 diabetes are part of a long list of "lifestyle" diseases that were rare throughout human history but are now common. A key idea from anthropology and evolutionary biology...

Globally, we are witnessing the rise of complex, non-communicable diseases (NCDs) related to changes in our daily environments. Obesity, asthma, cardiovascular disease, and type 2 diabetes are part of a long list of "lifestyle" diseases that were rare throughout human history but are now common. A key idea from anthropology and evolutionary biology...

Bipedal walking is the most common human gait, yet multiple lines of evidence indicate that there was also selection for endurance running in the hominin lineage. To evaluate if and how selection for running influenced the evolution of the human foot, we use functional, comparative, and fossil evidence to assess the three major biomechanical challe...

In humans, plantar cutaneous mechanoreceptors provide critical input signals for postural control during walking and running. Because these receptors are located within the dermis, the mechanical properties of the overlying epidermis likely affect the transmission of external stimuli. Epidermal layers are highly adaptable and can form hard and thic...

We examined the effects of vertical load placement on the metabolic cost of walking. Twelve healthy participants walked on a treadmill with 13.8 and 23.4 kg loads in both high and low vertical positions. Metabolic rate was measured using respirometry. While load position had no effect on the net metabolic rate for the 13.8 kg load, the net metaboli...

Humans differ from African great apes in numerous respects, but the chief initial difference setting hominins on their unique evolutionary trajectory was habitual bipedalism. The two most widely supported selective forces for this adaptation are increased efficiency of locomotion and improved ability to feed in upright contexts. By 4 million years...

Despite aerobic activity requiring up to tenfold increases in air intake, human populations in high-altitude hypoxic environments can sustain high levels of endurance physical activity. While these populations generally have relatively larger chest and lung volumes, how thoracic motions actively increase ventilation is unknown. Here we show that ri...

Research among non-industrial societies suggests that body kinematics adopted during running vary between groups according to the cultural importance of running. Among groups in which running is common and an important part of cultural identity, runners tend to adopt what exercise scientists and coaches consider to be good technique for avoiding in...

Evidence for Exercise in MedicineGuseh, Lieberman, and Baggish launch a new review series on exercise in medicine for NEJM Evidence by describing the epidemic of physical inactivity and examining the evidence for the therapeutic use of exercise.

Extensive research has shown that interleukin 6 (IL-6) is a multifunctional molecule that is both proinflammatory and anti-inflammatory, depending on the context. Here, we combine an evolutionary perspective with physiological data to propose that IL-6’s context-dependent effects on metabolism reflect its adaptive role for short-term energy allocat...

The proximate mechanisms by which physical activity (PA) slows senescence and decreases morbidity and mortality have been extensively documented. However, we lack an ultimate, evolutionary explanation for why lifelong PA, particularly during middle and older age, promotes health. As the growing worldwide epidemic of physical inactivity accelerates...

Objective Previous studies have demonstrated that low physical activity levels during youth are associated with the development of thin knee cartilage, which may increase susceptibility to osteoarthritis later in life. Here, we propose and test the hypothesis that reductions in physical activity impair knee cartilage growth among people in developi...

Objectives High trunk muscle endurance, strength, and moderate flexibility reportedly help maintain musculoskeletal health, but there is evidence for tradeoffs among these variables as well as sex differences in trunk muscle endurance and strength. To test if these observations extend similarly to both men and women in nonindustrial and industrial...

Objectives Brachial index is a skeletal ratio that describes the relative length of the distal forelimb. Over the course of hominin evolution, a shift toward smaller brachial indices occurred. First, Pleistocene australopiths yield values between extant chimpanzees and humans, with further evolution in Pliocene Homo to the modern human range. We hy...

To test the effects of domestication on craniofacial skeletal morphology, we used three-dimensional geometric morphometrics (GM) along with linear and endocranial measurements to compare selected (domesticated) and unselected foxes from the Russian Farm-Fox Experiment to wild foxes from the progenitor population from which the farmed foxes are deri...

Objectives The main objective was to test the hypothesis of a neuromechanical link in humans between the head and forearm during running mediated by the biceps brachii and superior trapezius muscles. We hypothesized that this linkage helps stabilize the head and combats rapid forward pitching during running which may interfere with gaze stability....

Like other animals, humans use their legs like springs to save energy during running. One potential contributor to leg stiffness in humans is the longitudinal arch (LA) of the foot. Studies of cadaveric feet have demonstrated that the LA can function like a spring, but it is unknown whether humans can adjust LA stiffness in coordination with more p...

Although most features of modern footwear have been intensively studied, there has been almost no research on the effects of toe springs. This nearly ubiquitous upward curvature of the sole at the front of the shoe elevates the toe box dorsally above the ground and thereby holds the toes in a constantly dorsiflexed position. While it is generally r...

Routine endurance exercise confers numerous health benefits, and high intensity exercise may accelerate and magnify many of these benefits. To date, explanatory molecular mechanisms and the influence of exercise intensity remain poorly understood. Circulating factors are hypothesized to transduce some of the systemic effects of exercise. We sought...

Response to: 'Is non-industrial society undergoing an energy balance transition predisposed to accumulate abdominal adipose tissue and susceptible to knee osteoarthritis?' by Yu et al

The Tarahumara (Rarámuri) are a Native American people from Chihuahua, Mexico, who have long been famous for running, but there is widespread incredulity about how and why they run such long distances. Some characterizations of Tarahumara running are also based on stereotypical views of athleticism among non-Western peoples, here labeled the “falla...

The plantar aponeurosis in the human foot has been extensively studied and thoroughly described, in part, because of the incidence of plantar fasciitis in humans. It is commonly assumed that the human plantar aponeurosis is a unique adaptation to bipedalism that evolved in concert with the longitudinal arch. However, the comparative anatomy of the...

Bipedal humans, like canids and some other cursorial mammals, are thought to have been selected for endurance running, which requires the ability to sustain aerobic metabolism over long distances by inspiring large volumes of air for prolonged periods of time. Here we test the general hypothesis that humans and other mammals selected for vigorous e...

Significance Unlike other great apes, humans evolved multisystem capabilities for moderate-intensity EPA, but it is unknown if selection acted similarly on the heart. We present data from a sample of humans, chimpanzees, and gorillas showing that the human (LV) evolved numerous features that help to augment stroke volume (SV), enabling moderate-int...

Non-industrial societies with low energy balance levels are expected to be less vulnerable than industrial societies to diseases associated with obesity including knee osteoarthritis. However, as non-industrial societies undergo rapid lifestyle changes that promote positive energy balance, individuals whose metabolisms are adapted to energetic scar...

Until relatively recently, humans, similar to other animals, were habitually barefoot. Therefore, the soles of our feet were the only direct contact between the body and the ground when walking. There is indirect evidence that footwear such as sandals and moccasins were first invented within the past 40 thousand years¹, the oldest recovered footwea...

Stereotypically, walking and running gaits in humans exhibit different arm swing behavior: during walking, the arm is kept mostly straight, while during running, the arm is bent at the elbow. The mechanism for this behavioral difference has not been explored before. We hypothesized that a mechanical tradeoff exists between the shoulder joint and th...

Objective: To investigate whether and how a sedentary lifestyle contributes to knee osteoarthritis (OA) incidence and severity. Design: An experiment was conducted using Hartley guinea pigs, an established idiopathic knee OA model. To simulate a sedentary lifestyle, growing animals (n = 18) were housed for 22 weeks in small cages that restricted th...

https://meeting.physanth.org/program/2019/session50/wallace-2019-physical-inactivity-and-the-etiology-of-osteoarthritis.html

Humans differ in many respects from other primates, but perhaps no derived human feature is more striking than our naked skin. Long purported to be adaptive, humans' unique external appearance is characterized by changes in both the patterning of hair follicles and eccrine sweat glands, producing decreased hair cover and increased sweat gland densi...

Humans differ in many respects from other primates, but perhaps no derived human feature is more striking than our naked skin. Long purported to be adaptive, our species' unique external appearance is characterized by changes in both the patterning of hair follicles and eccrine sweat glands, producing decreased hair cover and increased sweat gland...

The prevalence of osteoarthritis (OA) is rising for reasons that are not fully understood. In this Opinion article, we review the possibility that OA is an evolutionary mismatch disease, which is a disease more common today than in the past because genes inherited from previous generations are inadequately or imperfectly adapted to modern environme...

Adaptive explanations for modern human foot anatomy have long fascinated evolutionary biologists because of the dramatic differences between our feet and those of our closest living relatives, the great apes. Morphological features, including hallucal opposability, toe length and the longitudinal arch, have traditionally been used to dichotomize hu...

During locomotion, each step generates a shock wave that travels through the body toward the head. Without mechanisms for attenuation, repeated shocks can lead to pathology. Shock attenuation (SA) in the lower limb has been well studied, but little is known about how posture affects SA in the spine. To test the hypothesis that lumbar lordosis (LL)...

Despite substantial recent interest in walking barefoot and in minimal footwear, little is known about potential differences in walking biomechanics when unshod versus minimally shod. To test the hypothesis that heel impact forces are similar during barefoot and minimally shod walking, we analysed ground reaction forces recorded in both conditions...

The longitudinal arch (LA) helps stiffen the foot during walking, but many people in developed countries suffer from flat foot, a condition characterized by reduced LA stiffness that can impair gait. Studies have found this condition is rare in people who are habitually barefoot or wear minimal shoes compared to people who wear conventional modern...

An evolutionary perspective helps explain a conundrum faced by sports neurologists: why is the human brain dependent on physical activity to function optimally, yet simultaneously susceptible to harm from particular types of athletics? For millions of years, human bodies and brains co-evolved to meet the physical and cognitive demands of the unique...

If Wolff's law is valid, then quantifying the three-dimensional architecture of trabecular bone, specifically 3D principal trabecular orientation (3D-PTO), can reveal joint loading direction among different taxa. This study measured the architecture of trabecular bone in the 3rd metacarpal head of humans and chimpanzees, and then tested their assoc...

Purpose: The aim of this research is to assess foot structure, foot function, injury and physical activity levels in Kenyan children and adolescents who are HB compared with those who were habitually shod (HS). Methods: Foot structure, function, injury prevalence, and physical activity levels were studied using two studies with equal numbers of...

Significance Although nasal cavities fulfill similar tasks across animals, their geometry varies widely. One such task is heating and humidifying the inhaled air, which works best if the nasal cavity is narrow. However, narrow geometries have a large resistance to flow. We show that these opposing geometrical requirements are critical for shaping t...

Significance Knee osteoarthritis is a highly prevalent, disabling joint disease with causes that remain poorly understood but are commonly attributed to aging and obesity. To gain insight into the etiology of knee osteoarthritis, this study traces long-term trends in the disease in the United States using large skeletal samples spanning from prehis...

Objectives: Lumbar lordosis (LL) is a key adaptation for bipedalism, but factors underlying curvature variations remain unclear. This study tests three biomechanical models to explain LL variability. Materials and Methods: Thirty adults (15 male, 15 female) were scanned using magnetic resonance imaging (MRI), a standing posture analysis was condu...

Fossil evidence suggests considerable lordosis variability within and between hominin populations. However, interpreting these variations is challenging because the functional consequences of lordosis remain unclear. Although lordosis is crucial for postural stability, a complementary hypothesis predicts that lordosis represents a dynamic compromis...

Despite persistent critiques that many hypothesized adaptations are spandrels, a majority of evolutionary biologists accept that organisms are replete with adaptations: derived, novel features selected to improve reproductive success. Even so, testing hypotheses about adaptations is tricky for fossil taxa because one can only infer if a hypothesize...

Objectives To study the effects of urbanization on physical fitness (PF), we compare PF between urban and rural children from western Kenya. We hypothesize that active rural children are stronger, more flexible, and have greater endurance, and that PF differences are predictive of endurance running performance. Methods We recruited an age-matched,...

If Wolff’s law is valid, then quantifying the three-dimensional architecture of trabecular bone, specifically principal trabecular orientation (PTO), can reveal locomotor behavioral differences among different taxa. This study measured the architecture of trabecular bone in the 3rd metacarpal head of humans and chimps, and then tested their correla...

The origins of the genus Homo are murky, but by H. erectus, bigger brains and bodies had evolved that, along with larger foraging ranges, would have increased the daily energetic requirements of hominins. Yet H. erectus differs from earlier hominins in having relatively smaller teeth, reduced chewing muscles, weaker maximum bite force capabilities,...

If Wolff's law is valid, then quantifying the three-dimensional architecture of trabecular bone, specifically principal trabecular orientation (PTO), can reveal locomotor behavioral differences among different taxa. This study measured the architecture of trabecular bone in the 3rd metacarpal head of humans and chimps, and then tested their correla...

Endurance runners are often advised to use 90 strides min−1, but how optimal is this stride frequency and why? Endurance runners are also often advised to maintain short strides and avoid landing with the feet too far in front of their hips or knees (colloquially termed ‘overstriding’), but how do different kinematic strategies for varying stride l...

Significance Humans have the highest density of eccrine sweat glands of any mammal. Alongside hair follicles, eccrine glands are found throughout human skin and are indispensible for thermoregulation. Despite their importance, little is known about the biological factors that control eccrine gland formation and density. We investigated the genetic...

Runners are often categorized as forefoot, midfoot or rearfoot strikers, but how much and why do individuals vary in foot strike patterns when running on level terrain? This study used general linear mixed-effects models to explore both intra- and inter-individual variations in foot strike pattern among 48 Kalenjin-speaking participants from Kenya...

An evolutionary perspective helps evaluate the extent to which exercise is medicine and to explain the exercise paradox: why people tend to avoid exercise despite its benefits. Many lines of evidence indicate that humans evolved to be adapted for regular, moderate amounts of endurance physical activity into late age. However, because energy from fo...

This study examines whether the human iliotibial band (ITB) is specialized for elastic energy storage relative to the chimpanzee fascia lata (FL). To quantify the energy storage potential of these structures, we created computer models of human and chimpanzee lower limbs based on detailed anatomical dissections. We characterized the geometry and fo...