Human evolution: the discipline that can save the biosphere

orangutan

Understanding where we fit into the natural world and how, rather than rising above it, we depend on it like every other species, is a sobering realisation achieved through archaeological and anthropological research.

I recently wrote two articles for the Nature blog ‘Eyes on Environment’ arguing that this psychological revolution could be the only way to save the biosphere and ultimately, ourselves:

Part I

http://www.nature.com/scitable/blog/eyes-on-environment/human_evolution_the_discipline_that

Part II

http://www.nature.com/scitable/blog/eyes-on-environment/human_evolution_the_discipline_that_228236

Comments encouraged

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South Africa: a home more ancient than anyone thought

To an archaeologist, anthropologist or geneticist, South Africa is irresistible

And to tantalise the scientific tastebuds even further, two studies which came out this week and last have found that South Africa holds an even more ancient human history than anyone thought.

1. Little Foot

Australopithecus prometheus

In case you didn’t know, it is this country which has yielded some of the oldest and most significant fossil humans (hominins) found to date. The majority of these human relatives have been unearthed from the cave systems in Sterkfontein, Malapa, Taung and Swartkrans in Gauteng – including the famous ‘Mrs Ples’ and ‘Taung Child’ (Australopithecus africanus), Paranthropus robustus, and Australopithecus sediba.  These extinct South African human species date back to early days in human evolution; from ~3 to ~1.2 million years ago, though were unlikely our direct ancestors (as indicated by the recent find of a 2.8myo jaw bone in Ethiopia belonging to our genus Homo).

In the 1990’s, a new Australopithecus specimen was dug up in Sterkfontein which didn’t fit into any of the Australopithecus species already described. ‘Little Foot’ (Australopithecus prometheus) as it’s been affectionately known, was dated to ~2.2myo (million years old) based on the flowstones in which the fossil lay, though this dating was controversial. 9 years later, a team has re-dated Little Foot to 3.67mya, indicating that this species of hominin lived 1.47 million years earlier than thought, and at the same time as the famous East African species Australopithecus afarensis (‘Lucy’). Clearly the early players in human evolution (the early australopiths) were far more wide-ranging and diverse than we thought. Though the oldest of the oldest hominins belong to east and central Africa, the South African hominin record gets pushed back further in time.

2. The San

The San, or bushmen, are thought to be one of the oldest human lineages, still practising a hunter-gatherer existence in the Kalahari desert of Botswana and Namibia (though they’re being horribly repressed by the Botswanan government).

Mitochondrial DNA is an amazing piece of wizardry that evolutionary geneticists can use to track past population movements. Using mtDNA, previous studies have found that the San lineage broke off from that of every other human around 150,000 years ago, however a new study has re-analysed this date finding that the distinct San haplogroup (the unique mitochondrial DNA group that the San belong to) ‘L0d’ diverged from the main human line ~172,000 years ago. That’s incredibly old! Considering that our species (Homo sapiens) only evolved ~200,000 years ago, you can see how ancient the San lineage is. It is, in fact, the oldest offshoot from the main human lineage (of those analysed in this study).

And so although South Africa may not be the ancestral land of all modern humans, it has sure been a hospitable host to evolving hominins for at least 3,670,000 years

500,000 year-old humans and me

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This is what you will find 45 minutes up the west coast from Cape Town

As beautiful as this landscape is, its what’s under the sand that is truly valuable.

Dig down even only 20cm through the white dune sand and you’ll find the start of a deep red layer of sand. This is an ancient landscape of history frozen in time.

The site was originally discovered by workmen at the nearby nuclear power plant, who’s accidental unearthing of fossilised animal bones attracted Stanford archaeologist Richard Klein. After arriving on the scene and doing a fair bit of surveying and excavation, Klein et al. found that the find wasn’t an isolated stroke of luck – the site yielded wheelbarrows full of fossilised bones. Macro- and micromammals were present in their findings, ranging from the Egyptian mongoose (H. ichneumon), black rhino (D. bicornis), and the extinct long-horned African buffalo (Pelorovis antiquus), to the hairy-footed gerbil (G. paeba), Cape golden mole (C. asiatica), and Krebs’s fat mouse (S. krebsii), to name but a few. And that’s just the mammals! Bird species from the jackass penguin (S. demersus) to the spotted eagle owl (B. africanus) have appeared from the depths, as well as species of frogs and toads.

mnw2_buf_ill

P. antiquus (Image: E. Esterhuizen)

 

The incredible (and unexpected) biodiversity found in this stratigraphy is only really comparable to that in an Ace Ventura movie.

The abundance of bones from fresh water-dwelling animals (including hippos) reveal that this area, now vast dry sand dunes, was once a marshy wetland, with the high frequency of fauna that graze rather than browse (like buffalo), and fossilised pollen in hyena poo, indicating that the area was vast grasslands (full paper here).

However, the most exciting finds were those directly made by humans. Hundreds of stone tools have been gradually exposed in the form of flakes (and their debris), hammerstones and cores, showing that humans were living alongside this oasis of life. The Klein team conducted ‘optically stimulated luminescence dating’ on the sand surrounding the upper layer, arriving at a date of ~270,000 years ago. Tools have been found in lower layers too that go back even further in time – perhaps even ~500,000 years ago, or older. This would instantly get any archaeologist, anthropologist or biologist excited, as these humans were therefore pre-Homo sapiens (us). Most likely Homo erectus or Homo heidelbergensis, this realisation has transformed this site into a sought-after hominin site, allowing us to peer directly into the lives of our half a million year-old ancestors.

Cruz-Uribe et al., 2003

Cruz-Uribe et al., 2003

H. heidelbergensis

H. heidelbergensis

H. erectus

H. erectus

In a stroke of luck, I managed to get on board with a team carrying out new excavations at this same site, and what treasures we have found… Unfortunately I can’t reveal most of them, but I’ll provide a brief flavour to give you an idea.

The frequency of faunal finds only increased since we started, with a fossilised rhino tooth, antelope jaw, and possible extinct long-horned buffalo horn. Of greater significance in relation to humans, we’ve found lots of stone tools thereby confirming that hominins were hunting and living in this exact area.

What blew my mind after hours scraping away in a 1 x 1 meter hole however, was finding stone tools in situ myself. It’s hard to describe the feeling when you take it out of the sand, brush it off, hold it in your hand, and know that the last person to hold it was an extinct species of human living ~500,000 years ago. And boy are they incredibly beautiful! Flakes of silcrete, quartzite and quartz that I’d just pulled out of the sand after lying there for an unimaginable time-span were still sharp, and with a careful eye it’s easy to see where the maker had hit it off the stone core (and sometimes where they had missed), as well as where they had touched up the edges to make it as sharp as possible (a ‘retouched flake’). These materials are not available in the immediate area, and so, along with river pebble tools we’ve also found, these hominins were fetching specific lithic material, bringing it back to this site, and knapping away. Debitage and flake chips that have turned up in our excavation pits in abundance, confirm that these early humans were sitting exactly where I was, creating sharp tools, but ~500,000 years earlier.

I found, and still find this fact absolutely unfathomable.

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The lead researcher, Dr Deano Stynder’s, research interests in the site are centered on reconstructing the palaeoenvironment through faunal and floral proxy material in order to infer what the landscape in which Middle Pleistocene hominins were living was like (particularly whether the biome was C3 or C4 dominated). Through this, he hopes to gain a greater understanding of the environmental pressures which shaped the ecology and behaviour of these early humans.

In addition to the excavation (and bucket carrying, and endless sieving), Dr David Braun (Uni of Cape Town & George Washington Uni) turned up to carry out some aerial photography by literally attaching a camera to a kite. This is a nice technique to get a broader view of your site and a spatial context of where you’ve excavated…and more importantly where you haven’t.

Further excavations at this unique treasure trove of human evolution will take place through the hottest part of the summer, potentially leading to the faunal bones found 500,000 years from now being those of dehydrated archaeology students…