Four discoveries that redefined human history in just one summer

Growing up in a more literarily and theologically inclined family, much of my paleoanthropological education came from back issues of National Geographic and outdated editions of Encyclopædia Britannica. I read Mary Leakey’s article about her discovery of the footprints at Laetoli in the April 1979 issue, and pored through earlier issues to find articles about her work at Olduvai Gorge — articles like one from October 1961 by her husband Louis S. B. Leakey titled “Exploring 1,750,000 Years into Man’s Past: A Noted British Archaeologist Tells of Dramatic Discoveries at Olduvai Gorge.” I desperately wanted to be a young Leakey boy like (future paleoanthropologist) Richard or (future statesman) Philip, seen with his parents in this photo from that article. Frankly, I’d have settled for being one of Mary Leakey’s ever-present dalmatians.

Photo: National Geographic

It seemed like every issue in the 60’s and 70’s highlighted some amazing discovery that reshaped our understanding of how our species emerged in Africa. As I’ve re-engaged with archaeology and human evolution over the last few years, at no time has there been such a rapid sequence of major announcements from across a spectrum of disciplines, based on work happening all over the world, as there seems to be right at this very moment.

With stacks of books about Neanderthals representing decades of perspectives as a lens into the historiography of paleoanthropology, I’ve most enjoyed learning about how our understanding of human evolution has itself evolved over the past century and a half. Erik Trinkaus and Pat Shipman’s The Neanderthals: Changing the Image of Mankind from 1992 provides a solid overview of that history, beginning with rivalries between French scientists like Georges Cuvier and Jean-Baptiste-Pierre-Antoine de Monet, Chevalier de Lamarck. (Your automatic response is likely to take the side of a regular-sounding guy named Georges over someone with four hyphenated first names and two de‘s, but you would be on the wrong side of scientific history.) Trinkaus and Shipman fail to arrive at the current scientific consensus that Chris Stringer and Clive Gamble elucidate in In Search of the Neanderthals just a year later, while somehow missing entirely the decades-long rivalry between François Bordes and Lewis Binford. Nevetheless, The Neanderthals is still the most comprehensive history of the subject I’ve read, superseded recently by Dimitra Papagianni and Michael A. Morse’s excellent (but much briefer) The Neanderthals Rediscovered: How Modern Science is Rewriting Their Story (2015).

Armed with a vaguely monomaniacal overview of the chronology of discoveries in paleoanthropology from Engis (the first, then-unrecognized Neanderthal skull) to Rising Star (Homo naledi), I’ll reiterate my assertion above that the last few weeks have seen a series of major discoveries at a previously unprecedented pace.

In May, Lee Berger and his team at Rising Star in South Africa finally announced direct dates for their Homo naledi fossils, placing them between 335,000 and 236,000 years ago, just short of the 195,000-year age for the oldest-known Homo sapiens fossils from Omo Kibish in Ethiopia. This raises the likelihood that small-brained H. naledi and our big-brained Homo sapiens could have co-existed as part of a diverse range of related hominin species in Africa during the Middle Stone Age.

Photo of Homo naledi reconstruction and skeleton (links to National Geographic video)

(I can also heartily recommend Berger’s up-to-the-minute new book Almost Human: The Astonishing Tale of Homo naledi and the Discovery That Changed Our Human Story published alongside the journal article in May.)

Less than a month later, a team including Jean-Jacques Hublin upped the ante with new dates based on thermoluminescence tests of fire-heated stone tools associated with the Jebel Irhoud Homo sapiens fossils excavated in the 1960s. Dates ranging between 315,000 and 286,000 years ago place anatomically modern humans more than 5,200 km across the continent from Omo Kibish, a hundred thousand years earlier. These new dates fundamentally change our understanding of when, and potentially where, anatomically modern humans may have evolved within Africa. Much debate remains, of course, on anatomical modernity vs. behavioral modernity, but the new dates have fascinating implications.

Homo sapiens jaw from Jebel Irhoud
Homo sapiens jaw from Jebel Irhoud (photo credit: Jean-Jacques Hublin)

Africa may be the cradle of both our genus and species, but discoveries that shed light on our species’ evolution and dispersal aren’t limited to Africa itself. Last week, Chris Clarkson and his team at the Madjedbebe rock shelter in northern Australia presented dates of 65,000 years or more (with even deeper layers containing artifacts potentially as old as 80,000 years) for tools used by early Aboriginal inhabitants.

Meanwhile, Aboriginal rock art in Kimberley, Western Australia has been dated to over 60,000 years ago, predating the great Aurignacian art of Chauvet by thousands of years. Both these dates challenge the generally accepted exodus from Africa a mere 50,000 years ago — the first Australians may have needed boats to get from Sundaland (the Malay peninsula, Sumatra, Borneo, and Java) to Sahul (New Guinea and Australia), but they certainly didn’t have airplanes to travel from Africa straight to Australia quite so quickly. (The picture of random individuals floated across 90 km distances accidentally clinging to palm tree logs is frankly just racist…)

Finally, for the moment, research on a new mitochondrial DNA sequence (only the eighteenth Neanderthal individual sequenced so far) place the date for Neanderthal-Homo sapiens interbreeding far deeper in time, as early as 270,000 years ago. Like the new dates for the Jebel Irhoud fossils announced in June, it pushes back the timeline for the very existence of Homo sapiens as a species, as well as our potential dispersal from Africa and interaction with Eurasian Neanderthal populations.

From “Deeply divergent archaic mitochondrial genome provides lower time boundary for African gene flow into Neanderthals” (Posth, et al 2017)

Now, I’m no Clive Gamble, one of the greatest minds working in paleoanthropology today. In Settling the Earth: The Archaeology of Deep Human History, Gamble takes all of the data then available (2013), from nearly two centuries of archaeology and paleontology across the world, throws it in a blender, and presents a work of academic molecular gastronomy. Gamble is nothing if not an iconoclast — one of the first traditional concepts he dispatches is the very concept of prehistory. As the title of the book itself articulates, there is deep human history beneath the shallow, post-Neolithic veneer of the past five to ten thousand years through which we see the world of even older pre-sapiens hominins.

Gamble also takes a global view to the question of how hominins and humans dispersed across the world, eliminating regional and continental boundaries to create five “Terrae” that defined the limits of hominin expansion at various stages over the last 2 million years, from the first emergence of the Homo genus in Africa to our first steps away from our home planet today. For example, lower sea levels during multiple cooler periods (not just the last Ice Age that ended 12,000 years ago) exposed huge expanses of land that enabled dispersal — Sunda in modern Southeast Asia, Doggerland in the North Sea, and of course Beringia familiar to American school children as the “land bridge” between Siberia and Alaska. These were not simply “land bridges” to get between modern geopolitical entities, but expansive, ecologically rich biomes in their own right. Gambles ideas challenged my preconceived notions about population dispersal as well as the intellectual and cultural capabilities of our ancestors, both archaic and modern.

Even without Gamble’s genius, it’s tempting to formulate hypotheses and what-if scenarios that synthesize the discoveries of the last few weeks. If humans were in Australia by 65,000 years ago, the first broadly successful dispersal could not have happened as late as 60,000 years ago. Might the “unsuccessful” population of modern humans excavated in the caves at Qafzeh and Skhul in Isreal who left Africa as much as 120,000 years ago and allegedly died out by 80,000 years ago (replaced by a Neanderthal population from the north, only to be joined by more modern humans from Africa again later) have been partially successful after all? Since modern humans were perfectly capable of building boats to colonize Australia, might the humans of Jebel Irhoud have also built boats to cross to Gibralter, thus providing the basis for the interbreeding evidenced by the German Neanderthal woman from 270,000 years ago? I’ll await the next Grand Theory of Paleoanthropology from the likes of Clive Gamble, Chris Stringer, Ian Tattersall, or Robin Dunbar.

This much we do know: We are a much older species than we thought we were a month ago, by as much as a hundred thousand years. We also ranged farther, earlier than we thought we had barely a week ago — farther across Africa, much earlier to Australia, and maybe even into Neanderthal Europe (at least with people carrying our genes).

What discoveries remain to be shared with the world throughout the rest of 2017 — or even just the rest of this summer?


I’ve linked above mostly to primary sources in journals, but as a lay reader I’m indebted to the excellent science reporting in the Guardian as my starting point. “Via” links follow:

At home in the Holiest of Holies

I’m reading archaeologist Gregory J. Wightman’s The Origins of Religion in the Paleolithic, and thinking hard about how we humans evolved over the past several million years with a “God-shaped hole” in our psyches. I haven’t found the answer yet, but Philosopher Alain de Botton suggested in a recent interview that it is culture that can serve to fill that genuine sense of void that many of us sometimes feel in our modern lives.

You only have to look at the architecture of libraries and theaters and universities that were built in the age of declining religion to understand that our ancestors sought to fill the gap by creating temples of art, temples of culture, temples of learning, where we would congregate as we had previously done in the temples of religion.

National Gallery & St. Martin-in-the-Fields

I have certainly sensed the numinous in the great museums of the world, among the graves of poets, composers, and scientists, and deep inside a Neolithic passage tomb.

Entrance stone at Newgrange

Culture and the knowledge that it’s built on — but, most importantly, the processes and methods that increase, transmit, and store that knowledge — represent all that is good and holy about our species. While museums that house our art and science are certainly worthy of reverence, for sheer density of knowledge it’s hard to find a better temple of culture than a library.

The Guardian recently published a gorgous photo essay (though I’m unable to re-share their photos) of the most beautiful libraries in America. I’m proud to say that two of these libraries are right here in Seattle. In fact, for the first three months after I started up my previous company’s new Engineering hub, my team and I met each Friday at the Seattle Central Library, designed by Rem Koolhaas and Joshua Prince-Ramus.

Seattle library main branch overhead

I haven’t yet visited the Suzzallo Library at the University of Washington, but its Gothic Revival architecture certainly evokes European cathedrals, proving Alain de Botton’s point about 19th-century architects of secular institutions.

MK03235 University of Washington Suzzallo Library

Since appending “5 more museums to visit before I die” to my list of favorite museums back in 2009, I’ve visited several of them (the Met in New York, the Prado) and it may be time for a new list that includes museums I hadn’t anticipated loving so much (MOMA, Museo Arqueológico Nacional in Madrid).

And the Guardian has provided a convenient list of new places for pilgrimage I hope to visit in my lifetime.

What Stephen Hawking missed about the nature of human intelligence in PBS’s “Genius”

Back in 2012, Stephen Hawking visited Seattle and I had the privilege of attending a lecture he gave titled “Brane New World.” Now, I know from a statistical standpoint that I’m above average in intelligence, and I’ve read widely and deeply in physics and cosmology — I read Einstein’s Relativity: The Special and the General Theory when I was 15. And yet, I struggled to follow pretty much anything Hawking talked about. On my own in the darkened auditorium, being a statistical “genius”[1] did not alone enable me to understand the concepts of M-theory in his lecture.

This week, PBS launched a new, six-part series titled “Genius with Stephen Hawking.” Hawking narrates, and the show follows a trio it describes as “ordinary people”[2] through a sequence of exercises and experiments in which they uncover key concepts in physics and cosmology.

Stephen Hawking

At the beginning of the first show, Hawking addresses the team as “my budding geniuses.” Over the course of the show, they successfully conclude that backwards time travel is impossible due to the fundamental laws of physics, while the rather counterintuitive forwards “time travel” (beyond our prosaic movement through the fourth dimension as we live our lives) is a very real possibility thanks to the effects of gravity on space-time. Because time itself travels more slowly the closer one is to a major gravitational source, traveling relative to such a source — toward or away — causes a desynchronization of how the traveler experiences time from the “absolute” time at the traveler’s point of origin. For example, orbiting the supermassive black hole likely at the center of our galaxy for a while without falling into the event horizon and then somehow managing to escape back out would give us the experience of leaping “forward” in time when we return. Finally, having proven that even “ordinary people” can reach the conclusions of the great scientific minds of history, Hawking ends the show with the imperative “Think like a genius.”

But there is a fundamental flaw in Stephen Hawking’s logic (well, at least the logic of the show’s writers — Hawking himself is not actually credited as a writer). Unlike my poor solitary brain in that dark theater here in Seattle, each of the teams on the shows that aired this week benefited from two of the evolutionary advantages that have enabled our species to walk, row, sail, and ultimately fly out of the confines of our ancestral homelands.

What the show fails to highlight, focused as it is on physics and cosmology rather than paleoanthropology or evolutionary biology, is that the participants are benefiting from distributed cognition and altruism — attributes innate to how the human mind works. By operating as a cooperative team, with access to the information and technology humans have built up over the past 200,000 years, they are able to arrive at the same innovative breakthroughs that individual geniuses have over the last 400 years of unbounded scientific discovery. Each team of “ordinary people” is also a diverse group, and they complement each other as they explore concepts in relativity, cosmic scale, and the probability of the existence of intelligent life beyond our solar system.

But even those singular geniuses of the past have acknowledged their debt to the work of previous thinkers. Isaac Newton famously said in 1676, “If I have seen further, it is by standing on the shoulders of giants.” Today, Hawking stands on Einstein’s shoulders, who stood on Newton’s shoulders, who stood on Copernicus’s shoulders. It’s geniuses all the way down!

Through education and technology, each of us benefits from the giants whose shoulders we stand on. This is no less true with my college degree and iPhone today than it was 43,000 years ago when our ancestors taught their children how to carve musical instruments from animal bones. Because we all benefit from the accumulated culture of our species, we are indeed able to be geniuses.

So Stephen Hawking tells us, “Think like a genius.”

Due to the ambiguity of plurality in the second person in English grammar, Hawking leaves it open to us to interpret whether he is speaking to each of us individually, or all of us collectively. I prefer to believe that he means the latter. We are all stronger, better, and ultimately smarter together. Human intelligence exists not merely at an individual level, but as a result of the tools, artifacts, information, and meaning that we carry with us from one generation to the next.

Yes, Professor Hawking, thanks to the brilliance of all those who’ve gone before, we will indeed think like one monumental, collective genius.


[1] What this means is that there are about 700 million people smarter than me in the world today. That’s a lot of people. I find the concept of individual genius essentially meaningless.

[2] C’mon, PBS, you just mean “non-scientists.”

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A Paleolithic typology joke

François Bordes on how to tell the difference between a Mousterian point and a convergent scraper:

The best way to decide is to haft the piece and try to kill a bear with it. If the result is successful, then it is a point; if not, then it should be considered a convergent scraper. One of the problems with this approach is that it can quickly exhaust the available supply of bears or typologists

– As paraphrased by André Debénath and Harold L. Dibble in Handbook of Paleolithic Typology: Lower and Middle Paleolithic of Europe (1994)

Grizzly

Grizzly by “Life as Art” on Flickr

The detritus of hominid existence

Debénath & Dibble on the sheer scale of what lies beneath:

Handaxe by John FrereImagine … that during the time of the Acheulian in Europe, which lasted for at least 500,000 years, there was a constant population of 5,000 active tool makers. Imagine also that each of these flintknappers made only ten bifaces per year and perhaps 100 flake tools. Even with such conservative parameters…, this would have resulted in the production of 25,000,000,000 bifaces and 250,000,000,000 flake tools, of which only a minuscule proportion has been collected during the history of Paleolithic research.

– André Debénath and Harold L. Dibble in Handbook of Paleolithic Typology: Lower and Middle Paleolithic of Europe (1994)