Where did we come from?

Where Did We Come From? is the title of a book written by Carl Zimmer in the wake of the discovery of the “hobbits” of Flores fifteen years ago. It was a very good popular introduction to human evolution.

According to Zimmer, our African ancestors parted company with the ancestors of chimpanzees and bonobos six or seven million years ago to begin developing an upright posture, tool use and, perhaps most importantly, language.

Our own species, Homo sapiens, evolved about 200,000 years ago and began spreading out of Africa 130,000 years ago, through Europe, Asia, Australia and, eventually, America. We lived alongside closely related species until comparatively recent times. Neanderthals reached Europe before we did and coexisted with us there until 28,000 years ago, if not later. The ‘hobbits’ of Flores, by far the most spectacular recent discovery in the field, survived as recently as 18,000 years ago, well after Homo sapiens had migrated through South Asia and the islands to Australia.

Given the pace of discovery in the field, Zimmer’s book is now somewhat outdated. This collection of recent articles introduces research which adds depth and complexity to Zimmer’s account without changing its broad outlines. I have assembled them here in evolutionary order. Each story is represented by its headline and an excerpt, followed by a link to the source.

Millions of years ago

Ancient fossil skull discovered in Ethiopia fills critical gap in human evolution

• A rare 3.8 million year-old skull found in Ethiopia is rewriting our understanding of the human family tree
• Previously, only fragments had been found of Australopithecus anamensis, the oldest-known member of a group that gave rise to the species made famous by the Lucy skeleton
• Analysis of the skull shows A. anamensis had a mix of features from primitive species as well as Lucy

https://www.abc.net.au/news/science/2019-08-29/ancient-fossil-skull-found-in-ethiopia-fills-human-evolution-gap/11444130

Earliest known skull of Homo erectus unearthed by Australian-led team

The earliest known skull of Homo erectus has been unearthed by an Australian-led team of researchers who have dated the fossil at two million years old …

The lead researcher Prof Andy Herries said the skull was pieced together from more than 150 fragments uncovered at the Drimolen Main Quarry, located about 40km north of Johannesburg in South Africa.

https://www.theguardian.com/science/2020/apr/03/earliest-known-skull-of-homo-erectus-unearthed-by-australian-led-team

Ancestors of Flores ‘hobbits’ may have been pioneers of first ‘human’ migration out of Africa

The Flores hominins were, more clearly than ever, rooted deep in that [family] tree: they could not be descendants of Homo erectus. They came from something more primitive – a close cousin of Homo habilis. But what was an ancient-looking hominin like this doing in Indonesia?

In the most widely accepted model of human evolution today, the first emergence of hominins out of Africa involved Homo erectus, and happened some time after 2m years ago. But Homo floresiensis raises the tantalising possibility of an earlier expansion of hominins – who were probably not-quite-Homo – out of Africa.

https://theconversation.com/ancestors-of-flores-hobbits-may-have-been-pioneers-of-first-human-migration-out-of-africa-76560

More than 100,000 years ago

The Australian Museum has lots more information about the hobbits at  https://australianmuseum.net.au/learn/science/human-evolution/homo-floresiensis/ Here are a couple of key points:

The human remains date from about 100,000 to 60,000 years old, but archaeological evidence (mostly associated stone tools) suggests H. floresiensis lived at Liang Bua from at least 190,000 to 50,000 years ago (recent dates published in Nature, March 2016). These dates make it one of the latest-surviving humans along with Neanderthals, Denisovans and our own species H. sapiens.

Most scientists that accept H. floresiensis as a legitimate species now think its ancestor may have come from an early African dispersal by a primitive Homo species similar in appearance to H. habilis or the Dmanisi hominins. This means that it shared a common ancestor with Asian H. erectus but was not descended from it.

In 2016, scientists announced they had discovered the lower jaw and teeth from at least one adult and possibly two children of what may be an early form of H. floresiensis. These fossils were found at Mata Menge, about 70kms east of Liang Bua cave on Flores and date to 700,000 years old.

A Shocking Find in a Neanderthal Cave in France

A rock structure, built deep underground, is one of the earliest hominin constructions ever found. By measuring uranium levels on either side of the divide, the team could accurately tell when each stalagmite had been snapped off for construction.

Their date? 176,500 years ago, give or take a few millennia.

“When I announced the age to Jacques, he asked me to repeat it because it was so incredible,” says Verheyden. Outside Bruniquel Cave, the earliest, unambiguous human constructions are  just 20,000 years old. Most of these are ruins—collapsed collections of mammoth bones and deer antlers. By comparison, the Bruniquel stalagmite rings are well-preserved and far more ancient.

https://www.theatlantic.com/science/archive/2016/05/the-astonishing-age-of-a-neanderthal-cave-construction-site/484070/

This startling story quickly earned a response in Nature by Prof Chris Stringer, Research Leader in Human Origins at the Natural History Museum, London:

A comment on the ‘Early Neanderthal constructions deep in Bruniquel Cave in southwestern France’

The remarkable discovery of different-sized ‘structures’ made from purposefully broken stalagmites deep within Bruniquel Cave, south west France, would be significant for any period of time, but at around 175,000 years, these must have been made by early Neanderthals, the only known human inhabitants of Europe at this time.

The purpose of the structures and concentrated combustion zones which are mostly on the broken stalagmites rather than on the ground remain enigmatic, but they demonstrate that some Neanderthals, at least, were as much ‘at home’ deep within the cave as at its entrance.

There are examples of human habitation 30 or 40 metres into the dark zones of caves from sites of this or even greater age in Africa , but the Bruniquel occupation is some ten times deeper into the cave, and shows constructions as complex as some made by modern humans only 20 or 30,000 years ago.

https://www.nhm.ac.uk/press-office/press-releases/comment-on-early-neanderthal-constructions-in-brunique-cave.html

Archaeology Places Humans in Australia 120,000-Years-Ago

Shell middens and a potential ancient hearth add to growing evidence of a much deeper human occupation period in Australasia (prehistoric Sahul).

A meticulously detailed 11 years research program has concluded that there is compelling evidence for a human presence 120,000 years at Moyjil, Point Richie, on the far south coast of Victoria.

http://ancientnews.net/2019/03/11/archaeology-places-humans-in-australia-120000-years-ago/

Tens of thousands of years ago

Scientists find evidence of ‘ghost population’ of ancient humans

Scientists have found evidence for a mysterious “ghost population” of ancient humans that lived in Africa about half a million years ago and whose genes live on in people today.

Traces of the unknown ancestor emerged when researchers analysed genomes from west African populations and found that up to a fifth of their DNA appeared to have come from the missing relatives.

Geneticists suspect that the ancestors of modern west Africans interbred with the yet-to-be-discovered archaic humans tens of thousands of years ago, much as ancient Europeans once mated with Neanderthals.

https://www.theguardian.com/science/2020/feb/12/scientists-find-evidence-of-ghost-population-of-ancient-humans

Neanderthal-Denisovan ancestors interbred with a distantly related hominin

Previous research has shown that modern Eurasians interbred with their Neanderthal and Denisovan predecessors. We show here that hundreds of thousands of years earlier, the ancestors of Neanderthals and Denisovans interbred with their own Eurasian predecessors—members of a “superarchaic” population that separated from other humans about 2 million years ago. The superarchaic population was large, with an effective size between 20 and 50 thousand individuals. We confirm previous findings that (i) Denisovans also interbred with superarchaics, (ii) Neanderthals and Denisovans separated early in the middle Pleistocene, (iii) their ancestors endured a bottleneck of population size, and (iv) the Neanderthal population was large at first but then declined in size. We provide qualified support for the view that (v) Neanderthals interbred with the ancestors of modern humans.

That’s the “Abstract” (the authors’ summary) of a scientific paper which is rather similar to the one on which the previous story is based. The whole paper can be read at https://advances.sciencemag.org/content/6/8/eaay5483

This is what mysterious ancient humans might have looked like

We know that mysterious ancient humans called Denisovans once lived alongside Neanderthals, thanks to a few bones and teeth recovered from a cave in Siberia. Now, for the first time, researchers have shared what they might have looked like. … the reconstruction is that of a young female Denisovan.

https://edition.cnn.com/2019/09/19/world/denisovan-first-look-scn/index.html

65,000-year-old plant remains reveal the diet of the earliest known Aboriginal Australians

Australia’s first people ate a wide variety of fruits, vegetables, nuts and other plant foods, many of which would have taken considerable time and knowledge to prepare, according to our analysis of charred plant remains from a site dating back to 65,000 years ago.

We already know the earliest Aboriginal Australians arrived at least 65,000 years ago, after voyaging across Island Southeast Asia into the prehistoric supercontinent of Sahul, covering modern mainland Australia, Tasmania and New Guinea.

https://www.australiangeographic.com.au/topics/history-culture/2020/02/65000-year-old-plant-remains-reveal-the-diet-of-the-earliest-known-aboriginal-australians/

Is an Aboriginal tale of an ancient volcano the oldest story ever told?

Long ago, four giant beings arrived in southeast Australia. Three strode out to other parts of the continent, but one crouched in place. His body transformed into a volcano called Budj Bim, and his teeth became the lava the volcano spat out.

Now, scientists say this tale—told by the Aboriginal Gunditjmara people of the area—may have some basis in fact. About 37,000 years ago, Budj Bim [in SW Victoria] and another nearby volcano formed through a rapid series of eruptions, new evidence reveals, suggesting the legend may be the oldest story still being told today.

The study raises a provocative possibility, says Sean Ulm, an archaeologist at James Cook University, Cairns, who was not involved with the work. “It is an interesting proposition to think about these traditions extending for tens of thousands of years.” But he and others urge caution, as no other stories passed down orally are believed to have survived that long. …

Aboriginal tales are already among the oldest known. In 2015, Patrick Nunn, a geographer at the University of the Sunshine Coast, Maroochydore, co-authored a study suggesting 21 communities around Australia have independently kept alive stories describing an episode of sea level rise that drowned parts of the coast. Nunn thinks those stories might be about 7000 years old. The Gunditjmara story would be more than five times as old.

https://www.sciencemag.org/news/2020/02/aboriginal-tale-ancient-volcano-oldest-story-ever-told

I vaguely remember being told about about indigenous histories of an eruption somewhere near Undara (I might even have heard it from one of the guides at Undara) and the Kinrara eruption – only 7000 years ago according to Wikipedia, although this site isn’t so precise about the date – seems to be a good possibility.

Humans did not drive Australia’s megafauna to extinction – climate change did

When people first arrived in what is now Queensland, they would have found the land inhabited by massive animals including goannas six metres long and kangaroos twice as tall as a human.

We have studied fossil bones of these animals for the past decade. …

It has been argued that the extinctions were due to over-hunting by humans, and occurred shortly after people arrived in Australia. However, this theory is not supported by our finding that a diverse collection of these ancient giants still survived 40,000 years ago, after humans had spread around the continent.

The extinctions of these tropical megafauna occurred some time after our youngest fossil site formed, around 40,000 years ago. The time frame of their disappearance coincided with sustained regional changes in available water and vegetation, as well as increased fire frequency. This combination of factors may have proven fatal to the giant land and aquatic species.

https://www.theguardian.com/science/2020/may/19/humans-australia-megafauna-to-extinction-climate-queensland

It is widely believed that the first people to colonise the Americas quickly  drove the megafauna to extinction but the time scales in Australia are much longer and not so well known. The first Australians may have co-existed with our megafauna for as long as 80,000 years if the Point Richie discoveries stand up to further examination. Tim Flannery may still have been right when he proposed, in The Future Eaters, that firestick farming was responsible; if so, the answer to the question is “both”, since people brought on the climate change which was responsible for the extinction.

Looking for context

Wikipedia has a beautifully organised and illustrated table of important hominid fossils from 7 million to 5000 years old, i.e., from the last common ancestor we share with chimpanzees, to Otzi the iceman, at https://en.wikipedia.org/wiki/List_of_human_evolution_fossils

In the light of the recent discoveries above, its key lessons seem to be (1) how few pieces of the puzzle we still have and (2) the extent of the overlap between different species of people from 300,000 to 40,000 years ago. Point (1) is, of course, the reason that a single discovery can radically change our understanding of our evolution.

Aside from the purely scientific aspects, our history raises fascinating questions about the borderlines between human animals and other animals – borderlines in consciousness and intelligence, and the ethical borderlines which guide our sense of our proper place in the environment.

4 thoughts on “Where did we come from?”

  1. This story from ABC News a few years ago raises intriguing speculations about the level of complexity of indigenous Australian people around 10,000 years ago, and amplifies some troubling questions about white Australians’ conventional history of the colonial period.

    An ancient Aboriginal site at a secret location in the Victorian bush could be the oldest astronomical observatory in the world, pre-dating Stonehenge and even the Great Pyramids of Giza.
    Researchers say the site could date back more than 11,000 years and believe the stone arrangement mapped out the movements of the sun. The site could also disprove the notion that first Australians were uniformly nomadic hunter-gatherers.

    https://www.abc.net.au/news/2016-10-12/aboriginal-astronomy-provides-clues-to-ancient-life/7925024

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