Caves and Tools

In Morocco (Africa) 120,000 years ago, a wildcat, a jackal, and a fox met in a cave. What were they doing there? And what do humans have to do with it?

Today’s post is about [human culture]. And fossils. Most of what I post here is about what fossils can tell us about how, when, and where an animal lived. Fossils can tell us so much about the biology of now extinct animals. But that’s not all they can tell us. In some cases, the bones record what happened after the animal died.

The cave location in Morocco, Africa. (Figure 1b from the paper)

The Contrebandiers Cave in Morocco has sediment layers inside that date back to 120,000 years ago. Caves make excellent shelters, so as animals and plants use the shelter or get trapped there, they are fossilized and can be discovered later. Within the Contrebandiers Cave, explorers found the fossilized bones of a golden jackal, sand fox, wildcat, and several cow-like animals.

Some of the animals found at the cave. (Attributions on the image, retrieved from Wikipedia)

But these animals were not just hanging out together, they had been brought there by the humans (Homo sapiens) that lived there at the time. According to the markings on their bones, the animals they hunted and brought back to the cave were skinned in order to make clothing. Clothing itself does not fossilize easily because the fur it was made from breaks down very quickly.

An example of how ‘spatulate’ scraping tools were made and how they were used. (Figure 4 from the paper)

The animal bones weren’t the only evidence of skinning. There were tools present in the cave as well. Tools made from animal bones and shaped in specific ways by ancient human hands. Humans today still use similar tools and methods for skinning, so we don’t have to guess what the tools were for. This cave preserves the oldest evidence of formal bone tools and the production of clothing by modern humans (Homo sapiens)in Africa.

Side note: This is the first scientific paper I’ve read that has an “Inclusion and Diversity” statement at the end. The authors state, among other important points, that they ‘actively worked to promote gender balance in our reference list.’ I am grateful that the journal includes that statement and for the author’s work.

Humans and the Last Ice Age

This week we will continue our discussion from last week about the last Ice Age. This time, about humans. How did we get to the Americas? And I’m not talking about Christopher Columbus, because we all know he encountered American Indians. But how did those first people arrive on this continent?

A new [article], published this week, takes us back to the last Ice Age, around 14,000 years ago. At this time, two large ice sheets, the Laurentide and the Cordilleran Ice Complex, were covering most of Northern North America. In some places, these ices sheets were up to 2 miles thick.

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The thickness of the ice sheets at different cities 21,000 years ago. From here.

These ice sheets made it impossible for people to walk from Easternmost Russia to Alaska, or from Alaska to Canada and the more southern parts of North America. So people had to wait for the ice sheet to melt before making it over to the Americas. Also, once the ice melted, it left a giant lake that needed to shrink before people could cross it. Before now, the timing of when this ice sheet opened was not well worked out.

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The Laurentide and Cordilleran ice sheets. From here.

This study took sediment cores from lakes (like we discussed [last week]) and looked at all the DNA, small organisms, pollen, isotopes, and the sediments themselves that were present in the cores to test how the environment was changing from 14,000 to 11,000 years ago. The authors found that before 12,600 years ago there was little to no plant life in this region. Between 12,600 and 11,600 years ago there was steppe vegetation present. This type of vegetation creates a habitat for many animals like elk, moose, jackrabbits, voles, birds, and fish.

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The steppe environment by J. Matternes.

After 11,500 years ago the lake had more green algae, but also had evidence for poplar trees in the area. These trees provide habitat and food for many animals, and wood for fires and tools for people. So the authors conclude that a corridor through the ice would have been present starting around 12,600 years ago, with enough plants and animals present to support humans.

One last piece of the puzzle makes the story more complicated. There are human artifacts in the Americas starting around 13,400 years ago. So how did those people get there? The authors think that there were 2 pulses of immigration to the Americas. An earlier one from the coast, and a later one through the ice sheet. As always, more information will help to answer these questions.

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Figure 4 from the paper showing the two migration routes and their potential timing. Kyr means thousand years ago.