Where did we come from?


One of the big questions is: “Where did we come from?” Well, thanks to a strange fusion of a few different sciences, we’re getting closer to finding out — and the answer is pretty surprising.

The scientists included palaeontologists (the fossil dudes), geneticists (the DNA dudes) and archaeologists (the dudes who try to understand artifacts from our human past).

So here we are today, Homo sapiens, the only species of human left. But 100,000 years ago, there were at least three different species of human, and possibly six. So, to understand this, let’s look at the timeline of our evolution.

Well, the story begins in Africa about six to eight million years ago, when there was the big split between the line that led to us, and the line that led to the chimpanzees. Around 2.6 million years, our ancestors had invented rock tools and had a brain around 400 to 500 cubic centimeters or cc.

Via evolution, the brain size gradually increased, and by around 600,000 years ago, our direct ancestor was Homo heidelbergensis. They were not that different from us — the brain was only about 100cc smaller, at around 1,200cc, and there’s very strong evidence that they had language.

Around 500,000 years ago, a group of hominins (almost certainly Homo heidelbergensis) walked out of Africa forever, heading north for Europe and Asia. By around 300,000 years ago, they had evolved into two different species.

Now, one species was the Neanderthals, who headed west, towards Europe. About 100,000 years ago, they got itchy feet and began spreading east, towards Asia. The last Neanderthals died out as recently as 30,000 years ago, in caves in Gibraltar. We’ve known about the existence of the Neanderthals for nearly two centuries.

The other species (who also descended from Homo heidelbergensis) headed east towards Asia. They are also our long-lost cousins, but we’ve known about them only since 2010, when some remains were found in a cave in the Altai Mountains. Now, these mountains are in Southern Siberia, about 2600 kilometres north of Dhaka, the capital of Bangladesh.

In the 18th century, a hermit named Denis lived in this very cave and in 2008, an archaeologist exploring this cave found a tiny 40,000 year-old bone. It was a chip of the middle section of a little finger and when DNA was analysed, there was a huge surprise — it was human, but it was not Neanderthal, and it wasn’t us, Homo sapiens. So this new species of extinct human was called Denisovan, after the hermit, Denis.

So getting back to our timeline, about a quarter-of-a-million years ago, there were at least three species of humans on the planet. There was Homo heidelbergensis, still hanging around in Africa, the Neanderthals who had gone West to Europe, and the Denisovans in the East.

Then, in Africa, by around 200,000 years ago, Homo heidelbergensis had gradually evolved into us, Homo sapiens and, about 65 to 70,000 years ago, Homo sapiens left Africa, and spread across the world. They walked into Europe, and, to a very limited degree, they interbred with the Neanderthals.

Now, by this time, the Neanderthals had walked across to the east, in fact, to that very same cave that Denis the Hermit lived in. But the Neanderthals never walked back into Africa. So, all of us, except for Africans, today carry some Neanderthal DNA. About 2.5 per cent of our DNA (excluding Africans) is Neanderthal DNA.

Early Homo sapiens, when they left Africa, about 65 to 70,000 years ago, also went East and West. To a limited degree, the early Homo sapiens interbred with the Denisovans. So today, in the Melanesians of Papua New Guinea and of Bougainville, and in the Australian Aborigines, there’s some Denisovan DNA — up to five per cent.

But these answers, of course, lead to more questions.

First, if our Homo sapiens ancestors bred with the Denisovans, you can see how the Australian Aborigines and the Melanesians could have some Denisovan DNA. But how come hardly anybody else in Asia has any Denisovan DNA?

Second, we know that there were a few other species of humans around in the past — such as the Neanderthals and the Denisovans, and almost certainly Homo floresiensis. Why did they die out?

We don’t know.

But, this cave, now it was home to the Neanderthals and the Denisovans and to us Homo sapiens and, not to mention, Denis the Hermit. Here’s the big question: What’s so great about this cave?

Thanks to Dr Karl


What do you think?

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s