Ancient thigh bone casts doubt on human origins
Archaeologists have discovered that DNA from a bone found in Spain is 400,000 years old and comes from a mysterious branch of the human family tree. What is our species’ true history?
Once upon a time – around six million years ago, in fact – a chimp-like creature roamed the forests of Africa. Over the generations, as the most intelligent specimens thrived and passed on their genes, the animal’s brain grew in size. Its posture grew more upright; it learned to make fire and use simple tools. Finally, around 200,000 years ago, it developed into the species we now call Homo sapiens – in other words, us.
Such is the story of evolution we are all familiar with. But scientists are increasingly discovering that the truth is far more knotty. Our development from apes, it seems, was less like a single straight shoot and more like a sprawling tree whose branches are twisted in bewildering ways.
Last week, archaeologists reported a surprising discovery that adds another complication to our mysterious history. In a Spanish cave known as the ‘Pit of Bones’, home to the remains of at least 28 hominids of unknown type, they had unearthed a surviving piece of mitochondrial DNA.
The first surprising discovery was the DNA’s age: it came from an organism that died 400,000 years ago, making it more ancient than anyone had guessed. The second was what the DNA contained: the bones resembled those of Neanderthals, but the genes were much closer to another hominid species whose existence was only recently discovered.
This species is known as Denisovans. And the recent discovery suggests that they may have mated with Neanderthals or their ancestors. These species may in turn have interbred with our human ancestors.
The conclusion? Homo sapiens may be a hybrid species. There is strong evidence for the theory that we are the product of interbreeding. Scientists now believe that all modern humans have DNA inherited from Neanderthals, and some of us have Denisovan genes as well.
This strange possibility changes our conventional understanding of how we came to exist. But our story is still shrouded in millions of years of mystery.
But others find reasons to celebrate our apeish ancestry. For most of history humans have put themselves in a unique category, distinct from all creation. Now we know that we are one branch of nature’s vast and spectacular family – and that’s a good thing.
When theories of evolution first gained currency in the 19th century, many people were disgusted by the idea that they were descended from the ancestors of chimps. The idea that our ancestors spoke in howls and grunts and swung from trees seemed like an affront to human dignity.
A century and a half on, most people accept this theory as scientific fact. But some remain perturbed by our lowly ancestry. What hope have we of rising above our bestial instincts when there is so little to separate us from beasts?
- ‘Man has no reason to be ashamed of having an ape for his grandfather,’ said the biologist Thomas Huxley in a famous 1860 debate over evolution. Do you agree with him?
- What (if anything) separates humans from all other animals?
- Write a short story from the perspective of an ancestor of Homo sapiens. What would their lives have been like? How would they have seen the world?
- Do some research and explain how Neanderthals differed from Homo sapiens.
Some People Say...
“Humans are where the falling angel meets the rising ape.’Terry Pratchett”
What do you think?
Q & A
- How might we evolve in the future?
- A difficult and interesting question. Britain’s beloved nature presenter David Attenborough recently made a splash by claiming that we are no longer evolving at all: around 99% of our young survive to adulthood and most of us pass on our genes, which leaves little room for natural selection.
- Was he right?
- Not entirely. We are probably still developing tolerance for milk, for instance, and resistance to various diseases. And genes that make us likely to have more children have a big advantage. But it may well be true that ‘cultural evolution’ has replaced genes as the principal motor of our development as a species.
- Homo sapiens
- Latin for ‘man who knows’ or ‘wise man’. The earliest Homo sapien remains found so far are around 195,000 years old.
- Sometimes used to describe all great apes (including chimpanzees, gorillas and orangutans). But in this case the word refers only to human-like animals who are more closely related to us than to chimpanzees.
- Mitochondrial DNA
- Deoxyribonucleic acid (DNA) is the molecule that provides genetic instructions and thereby determines the make up of all life on Earth. Mitochondrial DNA is found in the energy-processing part of each cell. Whereas most DNA is a combination of maternal and paternal genes, mitochondrial DNA is inherited only from the mother.
- A highly intelligent species that coexisted with Homo sapiens and used many of the same tools as early humans. Research conducted this week suggests that they also buried their dead.
- Denisovan genes
- Most commonly found in the Pacific islands between Australia and South Asia. It is not clear whether these genes came from humans mating with Denisovans or with Neanderthals who had inherited Denisovan genes.