New Post on Homo naledi From Darrel Falk and Deb Haarsma

Darrel Falk and Deb Haarsma have teamed up on a new post about the peculiar South African hominin, Homo naledi, a find on which I reported a few days back.  Darrel Falk:

This is a wonderful time to be studying human origins. Scholars used to think that there was a slow steady progression of one single species after another becoming more and more human-like through time. That’s not the way it was at all. Although these fossils give no evidence for when H. naledi went extinct, it’s clear it was our contemporary in Africa for at least a little while. There also were at least several other hominin species outside of Africa at that same time. Some members of our species migrated out of Africa to Eurasia about 70,000 years ago, only to find that Homo neanderthalensis and the related, but distinctive Denisovans were already there. At the same time, the primitive diminutive species, H. florisiensis, occupied an island in Indonesia, and H. erectus was in eastern Asia. Meanwhile, back in Africa, we know from genetic evidence that, in addition to H. naledi, another unknown hominin species was present and interbred with our species as recently as 30,000 years ago. So our lineage shared life on this planet with a whole set of other species up until just a few thousand generations ago.

A bit back, I wrote a BioLogos post where I examined the hominin diversity in the early to middle Pleistocene, in which I asked the question How Many Forms Were There?  In that post, I pointed out that our simplistic notions of hominin taxonomy needed to be seriously re-evaluated. Where we once upon a time thought that there was only one species of hominin between 3 and 3.5 million years ago, there may, in fact, have been anywhere from three to five.  It is becoming more likely that this is a pattern that characterizes human evolution, perhaps, all the way up to the ascendancy of modern humans.  If this is so, then Bernard Wood is correct, in that we have many, many more species throughout the range of human evolution than we thought.  This discovery will cause a radical rethink of how we interpret species in the human fossil record.  Witness the rise of systematics.

What Were They Building?

The Atlantic (and some other news outlets) is running a story about a remarkable discovery at Bruniquel Cave, in France, of a structure that was created by Neandertals living in the area.  Ed Yong writes:

Some 336 meters into the cave, the caver stumbled across something extraordinary—a vast chamber where several stalagmites had been deliberately broken. Most of the 400 pieces had been arranged into two rings—a large one between 4 and 7 metres across, and a smaller one just 2 metres wide. Others had been propped up against these donuts. Yet others had been stacked into four piles. Traces of fire were everywhere, and there was a mass of burnt bones.

These weren’t natural formations, and they weren’t the work of bears. They were built by people.

Recognizing the site’s value, the caver brought in archaeologist Francois Rouzaud. Using carbon-dating, Rouzaud estimated that a burnt bear bone found within the chamber was 47,600 years old, which meant that the stalagmite rings were older than any known cave painting. It also meant that they couldn’t have been the work of Homo sapiens. Their builders must have been the only early humans in the south of France at the time: Neanderthals.

One truly interesting thing about this find is that it was only made with the aid of torches, which means that the Neandertals who built the structure also had them.

The original discovery had taken place in 1999 but, as of yet, the stalagmites had remained undated. The story continues:

After drilling into the stalagmites and pulling out cylinders of rock, the team could see an obvious transition between two layers. On one side were old minerals that were part of the original stalagmites; on the other were newer layers that had been laid down after the fragments were broken off by the cave’s former users. 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.

Most of the burials and other artistic evidence we have from the Neandertals comes from between 50 and 70 thousand years ago, during the height of the “classic” Neandertals, in France and Germany. This discovery, which is thought by some researchers to be cultural or religious, pushes that back a good 100 thousand years.

We are learning a good deal about the hominins that occupied Europe during the Middle Pleistocene and it is surprising.   The recent analysis of the German site of Schöningen, was revelatory, in that it showed hominins living in a setting where there was division of labor, highly advanced communication system, the creation of advanced bone and stone implements and complex hunting 300 thousand years ago.  It is clear that, over the course of the next 200 thousand years, continued cognitive advances were made. “A plausible explanation is that this was a meeting place for some type of ritual social behavior,” says Paola Villa from the University of Colorado Museum.

More pieces of the puzzle. 

Humans and Meat

New research by Dan Lieberman and Katherine Zink strongly supports what we have suspected for quite some time, that a substantial change in diet of early hominins led to rapid evolution in brain size and social structure.  Brian Handwerk of Smithsonian writes:

After measuring chewing and biting in modern humans, scientists found that a diet that includes one-third raw meat requires far less chewing and bite force exertion than meals of tubers alone. The researchers suggest that with the advent of stone tools, ancient human relatives were able to tenderize their food and make it far easier to chew and digest.

“An important step was just using a simple stone tool to cut our meat and bash our vegetables,” says Harvard University evolutionary biologist Daniel Lieberman.

The idea that fire allowed humans to cook their food and soften it that way has been around for quite some time and arguments usually point to the widespread use of fire toward the end of the Middle Pleistocene as the point where this begins to happen. This is the first time I have seen this argument extended to the early Pleistocene.The article continues:

“If I gave you a piece of raw goat, you would just chew and chew it, like a piece of bubble gum,” Lieberman explains. “Human teeth don't have the kind of shearing ability that, say, dogs' teeth have, and that is necessary to break down meat. With human chewing it just stays in a clump, and studies have shown how that makes digestion far less efficient.”

Cooking makes it easier to chew meat, but evidence suggests that the regular use of fire for cooking didn't pop up until perhaps half a million years ago—far later than the changes to H. erectus. Also, evidence from archaeological and paleontological research points to a spike in human meat consumption by at least 2.6 million years ago.

However, we have plenty of evidence that hominins had begun making stone tools some 3.3 million years ago. Those tools could have been used as pounders to tenderize foods, a practice seen in modern chimps. Flaked tools can also slice foods into easily chewable pieces or remove skin, cartilage and other bits that are harder to chew.

“It's not a coincidence that the oldest evidence for eating meat shows up around the same time as tools,” Lieberman says. “We know that the evolution of meat-eating basically required stone tools. And that had a huge effect on our biology.”

When my wife makes a dish involving chicken breasts, the first thing she does is pound them.  This makes it much softer and easier to eat. 

This is one of the principle reasons I tend to regard arguments in favor of vegetarianism somewhat warily. It is simply not in our nature or physiology to be that way. You can be one, if you wish, but that is not the natural state of things.