A Review: First Steps: How Upright Walking Made Us Human, by Jeremy DeSilva

by Howard E. Friedman

“What walks on four feet in the morning, two in the afternoon and three in the evening?”

Ever since Sophocles wrote this riddle for the Sphinx to pose to Oedipus around 429 BCE the answer to the clever riddle has been tinged with a sad reality:we humans who begin life crawling “on four feet” before we advance to “two in the afternoon”, can expect infirmity and a cane to walk on “three in the evening” if we are lucky enough to live into old age. To Jeremy DeSilva, paleoanthropologist and expert on foot and leg bones, the fact that we are so vulnerable is in fact one of the reasons that we upright walking humans are so interdependent on one another. Four legged animals can still get around well enough if they lose a leg. Not so for us bipedal humans. Even a minor foot injury can disrupt daily activities and losing a leg can forever change a person’s life. As a podiatrist, I have seen this time and again.

Is walking on two legs then really such a good idea after all? First Steps grapples with this question as well as issues related to the history of bipedal ambulation, tracking its origins in the fossil record, probing how walking upright has affected us as individuals, as communities and and a species.

Professor DeSilva, who studies ancient hominin foot and leg bones around the world and teaches at Dartmouth University, begins by questioning the value of walking by noting that the fastest humans are still so much slower than many four legged mammals. (“Hominin” refers to those species related to or close to humans”. ) Walking on two legs then is not a speed advantage and it is even less energy efficient than the gait of certain long legged mammals. While there is no definitive answer, DeSilva mentions the most common suggestions: walking on two legs freed up our hands to carry food or children or throw objects like rocks as weapons or use tools like sticks for digging up roots. But as an anthropologist, DeSilva cannot accept a theory without proof. And therefore he takes his readers around the world to learn first-hand from the most important fossils found so far that yield some clues as to when and where we Homo sapiens began our upright walking journey. It is these up close and personal visits to famous anthropological sits where First Steps is strongest.

First stop is Addis Ababa, Ethiopia, to see and hold the 3.18 million years old bones of the oldest most complete skeleton of an upright walking hominin, a female named Lucy. DeSilva writes tenderly about this ancient being, stating that if he had a time travel ticket he would “go to Ethiopia and spend the day with Lucy…to see how she moved, to measure every detail of her walk…”. Both Lucy’s pelvic, ankle and foot bones are consistent with upright walking. Her ankle bones are a similar to modern Homo sapien bones and her toes bones “were long and slightly curved, they had an upward tilt, indicating that she pushed off the ground with her toes like a human does while walking,” DeSilva writes. While Lucy’s knee was crushed when it was found, a fossilized knee found nearby of a similar age had an angulation of the end of the femur, called the bi-condylar angle, that is only found in bipedal walkers. Of particular interest to anthropologists however, is that while Lucy’s skeleton supports the fact that she walked upright, her skull size is still associated with a quite small brain. This is evidence, DeSilva writes, that walking on two legs preceded the large brain size we find in modern humans. And therefore, he concludes, “Lucy is the starting point for all we think we know about human evolution.”

To DeSilva’s credit a one-page very understandable evolutionary tree is printed at the front of the book for easy reference. Lucy, an Austrolapithicus afarensis, is on a limb that branches off of the main trunk that ultimately leads to Homo sapiens. Before and after that branch are other hominins with names less familiar such as Sahelanthropus, Ardipithecus and closer in time to us, Homo naledi, Denisovans and Neandertals. Branching off the main trunk toward the beginning of evolutionary time are chimpanzees, bonobos and gorillas.

But fossilized bones can only tell part of the story. Footprints are the image that is worth a thousand words.

In June 2019 DeSilva together with a colleague and a team of students discovered a hominin foot print in the Laetoli region of Tanzania near the Olduvai Gorge, a site famous for discoveries made by Mary Leakey in 1976. Other human like footprints had been found nearby and these newest footprints were further evidence of a bipedal gait now dating back over 3 million years. Heel toe. Heel toe. Some of the footprints found at Laetoli are of what appears to be a group of both adults and children walking together. It is tantalizing to imagine a family walking together millions of years ago like families still do today.

In the first half of First Steps, DeSilva details the hardware of walking, the ancient foot and leg bones and other skeletal modifications we have that facilitate walking on two feet. In the second half of the book, he writes about the software of bipedality and here he relies on various behavioral experts and other scientists. He begins this section looking at how babies learn to walk and the cultural variability around the world of what we consider a normal age to begin walking. In Western countries we expect toddlers to begin walking somewhere around 12-15 month or even a bit later. The Ache peoples, indigenous to Paraguay, carry their infants for the first two years and the children do not begin walking until that time. In contrast, in parts of Kenya and Uganda, DeSilva writes, infants begin walking around 9 months, due in part to their diligent mothers and grandmothers who massage the infants legs to help “improve motor coordination and strength”, he writes.

Prior to walking however, we need to be born and for that we need to be able to pass through the limited space available in the birth canal, itself limited by shape of the pelvis. Since human women are bipedal, the size of the pelvis has to be not so large as to impede normal walking yet large enough to facilitate birth. Four-legged animals do not have this restriction. Since the appearance of an influential article in Scientific American in 1960, anthropologists have posited that the fetus had to be born undeveloped enough that the large brain size could still fit through the pelvis, creating evolutionary pressure to favor smaller newborns and the women who gave birth to them. And furthermore, women with wider hips were thought to require greater amounts of energy when walking and certainly when running due to their anatomy. This theory though has been disproven thanks to a nearly complete pelvis found in Kebara Cave in Israel, a Neanderthal skeleton dated to about 60,000 years ago. The large size of the hip did not support a compromised gait, according to Cara Wall-Scheffler of the University of Cambridge, who studied the pelvis. Separately she noted that women of the Hazda hunter gatherer tribe walk about 6 miles a day. How could they do that with an inefficient gait she wondered? She ultimately proved that the energy required for a woman to carry a baby sized object is reduced in women with wide hips who can carry the child on the side of their body, resting it on the hip bone. Furthermore, the wide hips allow women who typically have shorter legs than men to have a longer stride. Further disproving the notion that women’s wide hips impair their gait, DeSilva cites the increasing frequency with which women continue to beat men in ultramarathons like in the 135 mile Badwater race through Death Valley and the 240 mile Moab ultramarathon. Women with wide hips, it turns out, can give birth and run fast for long distances.

DeSilva explores the uniqueness of individual human gait and interviews some of the researchers who are developing software for gait recognition. Professor Oscar Costilla-Reyes of MIT, for example, has developed an algorithm to identify people with over 99% percent accuracy by analyzing their footprints. And while gait analysis as a means to identify individuals may be too expensive or difficult for governments to implement, subtle changes in an individuals gait can indicate neurological changes signaling for example, dementia or Alzheimer’s. Intriguing as well is research by professors Ari Zivotovsky and Jeffrey Hausdorff in Israel who showed that middle school girls when walking together synchronize their gaits and do so even more when they hold hands!

In the final chapters of Foot Steps, DeSilva explores just how walking benefits us physically and mentally. He cites research that a daily walk can reduce the chance of developing breast cancer, possibly by reducing estrogen concentration in the blood. And he cites evidence that a daily walk of 30 minutes can lower the risk of coronary artery disease by 18 percent, writing that “coronary artery disease is all but unheard of among hunter-gatherers”. DeSilva further cites research that correlates increased daily walking to improved health in a group of 17,000 women with an average age of 72. The women who walked at least 4,400 steps a day had lower mortality than women who took 2,700 steps a day. And health benefits climbed as women walked even more. Walking has a long history of improving cognition too as DeSilva lists famous writers who took daily walks to help their creative process. It worked for William Wordsworth, Ralph Waldo Emerson and Henry David Thoreau among others. Brain MRI studies back up these findings. In one study, regions of the brain associated with creative thinking showed an increase in connectivity in the people who walked regularly. Another MRI study showed an increase in the size of the hippocampus in people who walked regularly compared to those who did not. The hippocampus is involved with learning and memory.

Of course, the news is not all good for us bipedal humans. Ask anyone who has torn their ACL ligament in the knee, had a total knee replacement, ankle fusion or sprained their ankle badly. The last injury is uniquely human as our primate cousins do not even have the anterior talo-fibular ligament which is the one we usually tear. Overall, however, Dr. DeSilva concludes, “The advantages of bipedal locomotion obviously outweigh the cost. Otherwise we would have gone extinct long ago.” But since we are among the few species that walk upright, “what tipped the scales toward survival rather than extinction”, he asks?

To answer that question DeSilva returns to the hardware of walking on two feet, a fossilized tibia from the Lake Turkana region of northern Kenya, dated to 1.9 million years ago. The tibia shows a healed fracture in an adult hominin. The fact that this ancient hominin survived strongly suggests, DeSilva writes, that her community supported her quite literally while she convalesced. And other ancient fossils also show healed fractures from serious injuries suggesting that this was not an isolated event. Having only one good leg to stand on made a limping individual dependent on other community members, and it seems their fellows rose to the occasion. While DeSilva argues that empathy was a prerequisite for our social species to develop as it did, as “the last bipedal ape on Earth” he writes, we should embrace “our capacity for empathy, tolerance and cooperation” and appreciate how those human attributes are intertwined with our most basic activity, walking on two feet.

Howard E. Friedman


Off the Trail: The Anthropocene is here to stay.

The term Anthropocene is starting to appear more and more frequently. The “cene” ending of the word is familiar from any number of geologic epochs such as Holocene or Pleistocene. But in the case of Anthropocene we humans are the subjects, not dinosaurs, or glaciers or seismic events of unimaginable proportion.

Scientists continue to try and understand how we humans, the “anthro” in Anthropocene, are impacting our planet. Are we causing irreversible changes with development? Or over-population? Or did we start to irrevocably alter the planet when we began agriculture more than 10,000 years ago, deforesting and tilling the earth?  And anthropology professor Dr. John Hawks has written about some anthropologists who wonder if we should capitalize the word at all or refer to our epoch with a little ‘a’ just to signal that this time period is currently unfolding and its full details can not yet be known.

Read below for two scientists thoughts on this topic after convening an expert panel to think and write about our current geologic era and try to determine where we can go from here in understanding the “Anthropocene” and the impact we are having on what is for now, at least, our solar system’s only known habitable planet.

Below is the beginning of the article which was published in theconversation.com and which I saw re-posted on earthsky.org. I encourage you to read the entire piece, written by Professors Ben A. Minteer and Stephen Pyne, both of Arizona State University.


What does it mean to preserve nature in the Age of Humans

“Is the Earth now spinning through the “Age of Humans?” More than a few scientists think so. They’ve suggested, in fact, that we modify the name of the current geological epoch (the Holocene, which began roughly 12,000 years ago) to the “Anthropocene.” It’s a term first put into wide circulation by Nobel-Prize winning atmospheric chemist Paul Crutzen in an article published in Nature in 2002. And it’s stirring up a good deal of debate, not only among geologists.

The idea is that we needed a new planetary marker to account for the scale of human changes to the Earth: extensive land transformation, mass extinctions, control of the nitrogen cycle, large-scale water diversion, and especially change of the atmosphere through the emission of greenhouse gases. Although naming geological epochs isn’t usually a controversial act, the Anthropocene proposal is radical because it means that what had been an environmental fixture against which people acted, the geological record, is now just another expression of the human presence.

It seems to be a particularly bitter pill to swallow for nature preservationists, heirs to the American tradition led by writers, scientists and activists such as John Muir, Aldo Leopold, David Brower, Rachel Carson and Edward Abbey. That’s because some have argued the traditional focus on the goal of wilderness protection rests on a view of “pristine” nature that is simply no longer viable on a planet hurtling toward nine billion human inhabitants.

Given this situation, we felt the time was ripe to explore the impact of the Anthropocene on the idea and practice of nature preservation. Our plan was to create a salon, a kind of literary summit. But we wanted to cut to the chase: What does it mean to “save American nature” in the age of humans?”

(the rest of the article can be accessed here)

On the Trail: Hiking alongside evolution

Tabun Cave, site of pre-historic human activity,  lies next to the Israel National Trail (phto: Albatross Aerial Photography)

Tabun Cave, site of pre-historic human activity, lies next to the Israel National Trail (phto: Albatross Aerial Photography)

Israel is in the news for the recently announced discovery of the Manot 1 pre-historic modern human partial skull, carefully dated to 55,000 years ago. The skull was found in a limestone cave in the Galilee region of northern Israel in 2008 and carefully researched for the past 6 years by Professor Israel Hershkovitz and a team of anthropologists from Tel Aviv University. The find was published in the respected journal Nature and reported widely across the world. The skull has features of modern humans but also some Neanderthal features, again focusing attention on the question: did ancient Homo sapiens interbreed with Neanderthals?

About one month ago I was fortunate to have an opportunity (thanks, Mom and Dad) to visit the Carmel region of Israel and hike a bit of the Israel National Trail, a hiking trail which extends the length of the country, 1000 km, from north to south.

Blue, white and orange triple color blaze of the Israel National Trail

Blue, white and orange triple color blaze of the Israel National Trail

The section of trail I visited is literally a stone’s throw from another important anthropology site, the location of Tabun, Skhul and El-Wad caves, also limestone massifs, with a commanding view of the Mediterranean Sea and Israeli coastline just 5-6 miles due west.

View of the Mediterranean from Nachal Meorot

View of the Mediterranean from Nachal Meorot

These caves were discovered and excavated beginning in the late 1920s by British paleontologist Dorothy Garrod,a pioneer and rare female in her field. The site continued to be excavated into the 1960s and was recently named a UNESCO World Heritage Site. This collection of caves demonstrates more than 200,000 years of human existence including Neanderthal and early Homo sapien remains, living in the same location, even if not at the same time.

Looking into Tabun cave. Neanderthal remains were found in the middle layers and ancient hominid remains above and below.

Looking into Tabun cave. Neandratal remains were found in the middle layers and ancient hominid remains above and below.

Moreover, one of the adjacent caves presents a clear example of Natufian culture, humans who began to settle in one location and live a more agrarian lifestyle, no longer living a nomadic ‘hunter-gatherer’ existence. Just outside this cave system were multiple buried human skeletal remains, more than 10,000 years old, decorated with various ornaments. These may represent one of the earliest burial sites in the world.

And now, just dozens of miles away, we now have evidence of human remains which indeed represent another example of ancient humans in transition. Just exactly what that transition was from and where it was going to remains to be proven more definitively.

Manot-1 partial skull with features of ancient hominid and Neandratal (photo: Prof. I. Hershkovitz, in Nature, on-line Jan. 2015)

Manot-1 partial skull with features of ancient hominid and Neanderthal (photo: Prof. I. Hershkovitz, in Nature, on-line Jan. 2015)

It is rare these days to see “Israel” in a newspaper headline without some human tragedy or geopolitical tragedy following close behind. For the story from Manot Cave, at least, the only controversy would be of a scientific nature. And on that point, remarkably, most scientists interviewed have praised the Tel Aviv University researchers for their careful, deliberate study, analysis and conclusions.

While most tourists who travel to Israel do so to visit and bask in the holy religious sites of the past couple of thousand years, be they Jewish or Christian or Muslim, very few people travel to Israel to see where ancient Neanderthals once lived. I myself have traveled to Israel on multiple occasions, and only recently even knew such a site existed in Israel (thank you Professor John Hawks and for your Coursera course on Human Evolution).

Perhaps after visiting all the holy sites, tourists and locals alike should visit these most ancient sites of human habitation, to underscore our common heritage and to know that what joins us all into the family of ‘Man’ is so much more ancient than what divides us.

Howard E. Friedman


To be or not to be Barefoot. Is that the Question?

English: Barefoot hiking south of Penzberg, Ge...

English: Barefoot hiking south of Penzberg, Germany (Photo credit: Wikipedia)

Barefoot running and barefoot hiking have been discussed continuously since at least May 2009 when Chris McDougall’s book Born to Run was published and fueled nationwide interest in running very long distances barefooted, or, at least with only a flexible piece of rubber under one’s foot and nothing more. McDougall chronicled the ultra long distance runs of the Tarahumara Indian tribe of Mexico who’s members, men, women and children routinely logged long distance runs in a type of sandal.

And barefoot running received a further boost in 2010 when Harvard Evolutionary Biology professor Daniel Lieberman published an article in the respected science journal  Nature  about foot strike patterns in habitually barefoot runners compared to shod runners. In fact, Dr. Lieberman’s work was cited in McDougall’s book.

And since that time ‘barefoot’ has been a hundred million dollar word.

Every major shoe manufacturer and many less well known have marketed ‘barefoot’ running shoes, admittedly an oxymoron, Dr. Lieberman has noted. The shoe sole manufacturer Vibram introduced the iconic Vibram Five Fingers  a cross between a glove and a rubber soled moccasin. New Balance and others heavily marketed ‘minimalist’ shoes invoking themes suggestive of running barefoot.

And bloggers and newly minted experts cropped up overnight inveighing the virtues of the barefoot gospel. If it was good enough for Austrolapithicus, it must be good enough for us, was a general sentiment. Indeed, the modern running shoe as we know it only dates back to the 1970s (of the common era). And even according to anthropologists  who date shoe wearing among Homo Sapiens as far back as 40,000 or so years (Trinkhaus and Shang,  “Anatomical evidence for the antiquity of human footwear”, Journal of Archealogical Science 2008), ancient man’s shoes surely did not include motion controlling ethyl vinyl acetate heel cushions and a thermal polyurethane reinforced arch support.

And so authors Tam, et. al of the Department of Human Biology at the University of Cape Town rightly questioned many of the commonly accepted notions about barefooted running in their October 2013 article, “Barefoot running, an evaluation of current hypothesis, future research and clinical applications”, in the British Journal of Sports Medicine published first on-line.

A woman wears Vibram "Five Fingers" ...

A woman wears Vibram “Five Fingers” shoes. (Photo credit: Wikipedia)

Tam, et. al thoroughly review much of what is known about barefoot running, making their article an important one for someone new to the discussion about this ongoing phenomenon. Their central question remains, however,  Does running barefooted reduce the rate of injuries? And toward that end they quote Daniel Lieberman from his most recently published analysis on the topic. “How one runs is probably more important than what is on one’s feet, but what is on one’s feet may affect how one runs”, Lieberman writes near the beginning of a 2012 article.

However, what Lieberman writes at the end of his lucid, organized and thorough review of barefoot running is perhaps more cogent. In “What We Can Learn About Running From Barefoot Running: An Evolutionary Medical Perspective”, published in Exercise and Sport Sciences Review (April 2012), he writes: “My prediction – which I readily admit is nothing more than hypothesis that could be incorrect – is that shod runners with lower injury rates have a more barefoot style form…Likewise I predict that injury rates are higher among barefoot runners who either lack enough musculoskeletal strength in their calves and feet…or who still run as if they were shod with long strides and slow stride frequencies.”

It seems than that many questions about barefoot running remain outstanding. But some truths have been established. Lighter weight shoes do reduce the oxygen need of the runner with a one percent decreased need for every 100 gm decreased weight of the shoes. A mid foot or forefoot strike avoids the high pressure impacts of a heel strike. And shorter strides with a higher frequency cadence do seem to be correlated with a reduction in injuries.

So while one is vacillating about what shoes to buy, in the meanwhile run like a hunter gatherer may (or may not) have run: shorten your stride, land on the middle or front of your foot and increase the number of steps you take per minute. Unless of course you develop pain in your foot, leg, hip, back or elsewhere.  In that case, go back to whatever you were doing before!