Homo erectus Was Lazy??

A short piece in PhysOrg links to an article in PLoS that argues that, when faced with the opportunity to make Acheulean tools out of really good raw materials at a site in what is now Saudi Arabia, the local Homo erectus group took the easy way out and made them out of whatever was lying around.  From the PhysOrg piece: “New archaeological research from The Australian National University (ANU) has found that Homo erectus, an extinct species of primitive humans, went extinct in part because they were 'lazy'.”

First off, the first paragraph is nothing short of idiotic. There is absolutely no evidence whatsoever that Homo erectus went extinct because they were lazy. They colonized huge sections of Asia and were integral to the appearance of early modern humans in the area.They might have disappeared from this particular area of Saudi Arabia but that is all.  Also from PhysOrg:

"At the site we looked at there was a big rocky outcrop of quality stone just a short distance away up a small hill.

"But rather than walk up the hill they would just use whatever bits had rolled down and were lying at the bottom.

"When we looked at the rocky outcrop there were no signs of any activity, no artefacts and no quarrying of the stone.

"They knew it was there, but because they had enough adequate resources they seem to have thought, 'why bother?'".

This is in contrast to the stone tool makers of later periods, including early Homo sapiens and Neanderthals, who were climbing mountains to find good quality stone and transporting it over long distances.

Maybe this particular population was stressed in some way. Maybe the tools that they made were good enough to get done what they needed. Who knows. It is a huge inference, though, that because they didn't use the raw materials that were better that they were “lazy.”  The last sentence of the abstract reads thus:

The Acheulean hominins at Dawadmi were strong and skilful, with their adaptation evidently successful for some time. However, these biface-makers were also technologically conservative, and used least-effort strategies of resource procurement and tool transport. Ultimately, central Arabia was depopulated, likely in the face of environmental deterioration in the form of increasing aridity.

This sentence alone belies the opening, “lazy” paragraph of the PhysOrg story.  More junk journalism. 

New DNA Analysis Allows for Greater Understanding of Modern Human Prehistory

From Science Daily:

A University of Utah-led team developed a new method for analyzing DNA sequence data to reconstruct the early history of the archaic human populations. They revealed an evolutionary story that contradicts conventional wisdom about modern humans, Neanderthals and Denisovans.

The study¹ found that the Neanderthal-Denisovan lineage nearly went extinct after separating from modern humans. Just 300 generations later, Neanderthals and Denisovans diverged from each other around 744,000 years ago. Then, the global Neanderthal population grew to tens of thousands of individuals living in fragmented, isolated populations scattered across Eurasia.

"This hypothesis is against conventional wisdom, but it makes more sense than the conventional wisdom." said Alan Rogers, professor in the Department of Anthropology and lead author of the study that will publish online on August 7, 2017 in the Proceedings of the National Academy of Sciences.

As the authors note, there is mounting evidence of a migration from Africa to Europe, likely by way of the Strait of Gibraltar, in which Acheulean stone tools are introduced by a group which became known as Homo heidelbergensis.  This group, subsequently, split, likely gave rise to the Neandertals  and the Denisovans a bit later.  Then, a second wave of migrations around 90 to 100 ky happened, during which there was hybridization between Neandertals, moderns and Denisovans.

We live in a time where we now have the genomes of archaic Africans, Eurasians, Neandertals, Denisovans and early moderns and can compare them using site pattern analysis.  These authors found that

• In contrast to previous studies, this one indicates that Neandertal population size was large, on the order of tens of thousands of people, in isolated populations
• The split between the Neandertals and Denisovans was early, on the order of 744 thousand years ago.  
• By the time you find these hominins in the fossil record, they had already split from the Denisovans, which explains why the Atapuerca Sima De Los Huesos hominins resemble Neandertals more than Denisovans.
• Therefore, Neandertal features are thought to have emerged over a long period of time in Europe. 

This analysis will help us rethink our understanding of the fossil material from Gran Dolina, which now likely represents a population from which both the Denisovans and Neandertals split.  This makes sense, given the general, non-derived nature of the fossil material from there.  Things are slowly (maybe?) falling into place.

¹Alan R. Rogers, Ryan J. Bohlender, and Chad D. Huff. Early history of Neanderthals and Denisovans. PNAS, August 2017 DOI: 10.1073/pnas.1706426114

Genetic Data Indicates Another Migration of Archaic Homo sapiens Out of Africa

Ars Technica is running a story based off of a Nature Communications article about a migration of archaic Homo sapiens out of Africa that took place more recently than the one at c. 650 kya that was hypothesized to have given rise to the Neandertals. Cathleen O'Grady writes:

The picture painted by nuclear DNA (nDNA) is that, between 765,000 and 550,000 years ago, our ancestors in Africa diverged into two groups. One group would eventually lead to our own species, although we wouldn't make an appearance until around 200,000 years ago. The other group would lead to Neanderthals and the closely related Denisovans. This proto-Neanderthal/Denisovan group left Africa for Eurasia at some point; sometime around 430,000 years ago, they diverged into distinct Neanderthals and Denisovans.

But the picture painted by mtDNA is different. Neanderthal mtDNA is more similar to modern humans than it is to Denisovan mtDNA. And the divergence date between us and them, when estimated based on mtDNA, is much more recent—between 498,000 and 295,000 years ago.

Some researchers have suggested that you can explain this mixed genetic evidence if Neanderthals interbred with another, more recent African group of humans. This would provide them with different mtDNA after they split from Denisovans. And that, in turn, means that there must have been humans, closely related to our own species, who left Africa for Europe far earlier than previously suspected.

It is not such a stretch to suggest that the recent finds from Jebel Irhoud may be a population related to this mystery population.  The Jebel Irhoud crania show modern characteristics in the face and have been placed in the modern Homo sapiens clade (if provisionally).  Whether or not they have enough traits found in later humans to be the stem group of anatomically modern Homo sapiens is not currently known.  Jebel Irhoud is a hop, skip and a jump to Gibraltar, which we know had already provided an avenue of migration for earlier populations of early Homo which gave rise to Homo heidelbergensis in Europe.

As the story notes, there are remarkable similarities in stone tool technologies between the northern  African Middle Stone Age and the European late Acheulean and early Mousterian tools.  There are Levallois flakes found in both areas, as well as similarly-made knives and points.  This suggests that populations in North Africa had some contact with those of southern Europe.  As we push the age of the modern human clade back in time, these discoveries help to frame the appearance of modern humans and how they interacted with the populations around them.  Exciting times!

The Nature Communications article, Deeply divergent archaic mitochondrial genome provides lower time boundary for African gene flow into Neanderthals can be found here and was free when I read it.

400,000-Year Old Cranium Found in Portugal

A multinational research team has discovered a fossil human at the site of Aroeira, in Portugal.  From the story in EurekAlert:

The cranium represents the westernmost human fossil ever found in Europe during the middle Pleistocene epoch and one of the earliest on this continent to be associated with the Acheulean stone tool industry. In contrast to other fossils from this same time period, many of which are poorly dated or lack a clear archaeological context, the cranium discovered in the cave of Aroeira in Portugal is well-dated to 400,000 years ago and appeared in association with abundant faunal remains and stone tools, including numerous bifaces (handaxes).

The skull is considerably encrusted, still and much work will have to be done. It is long and low, with large brow ridges, a sloping forehead and a large occipital protuberance. It does not look like it has an angular torus, however. All of these characteristics are consistent with this date. Neat!

Here is the image from the short post.

Of Stone Tools and Human Cognition

One of the things that is taught in human origins classes all over the world is that the earliest stone tools were likely made at the site of Dikika, and date to around 3.4 million years ago.  That perspective has now been called into question with the observation that monkeys can create exactly the same kinds of tools—by accident. Sarah Knapton, writing in the Telegraph has this:

In a discovery that calls into question decades of research, a band of wild bearded capuchin monkeys in Brazil were seen hammering rocks to extract minerals, causing large flakes to fly off.

Previously archaeologists believed the flakes were only made by humans through a process called ‘stone-knapping’ where a larger rock is hammered with another stone to produce sharp blade-like slivers which can be used for arrows, spears or knives.

The flakes were thought to represent a turning point in human evolution because they demonstrated a level of planning, cognition and hand manipulation that could not be achieved by other animals.

But the new research suggests that flakes can be made without any such foresight. In fact they can simply be made by accident.

“The fact that we have discovered monkeys can produce the same result does throw a bit of a spanner in the works in our thinking on evolutionary behaviour and how we attribute such artefacts,” said Dr Michael Haslam, lead of the Primate Archaeology project at the University of Oxford.

This is possible and it may be that some of the earliest “tools” aren't any such thing. When hominins started using tools in a concerted fashion has always been a large question in the evolutionary picture. It is very clear that by what we know as the Acheulean, manufactured by Homo ergaster, Homo erectus and Homo heidelbergensis, the hand axes are clearly human-made. Before that, maybe more research needs to be done to verify that what we think is human behavior actually is.  It is natural to want to impart human intelligence to our ancestors as far back as we can, in an effort to “humanize” them but, sometimes, this might be just wishful thinking.