Oldest DNA Shares Earliest Modern Humans’ Secrets
The thigh bone of an ancient man that was found in Siberia has yielded some answers about the beginning of modern humans, published in Nature.
The man is one of the earliest modern humans to have been discovered in Eurasia (the combined land mass of Europe and Asia), dating back around 45,000 years.
A genome sequence taken from collagen teased from the bone – which helps to determine a person’s complete DNA sequence – shows that modern humans occurred for the first time between 50,000 and 60,000 years ago.
The analysis also raises the possibility that the very first human line actually emerged millions of years earlier than previously thought.
The work was carried out by a team from Leipzig’s Max Planck Institute in Germany, led by Professor Svante Paabo.
The team developed methods that enabled them to extract and read the genetic code of DNA from ancient human remains. From this, they were able to unravel the story of modern humans as they spread across the world.
Back in 2010, the same team published research that showed that all humans around today – except for those from Africa – have a tiny piece of Neanderthal DNA. This DNA has been broken into smaller and smaller chunks over each generation.
By analysing the size of these chunks going backwards, incorporating the 45,000-year-old’s data into the equation, the team was able to calculate when Homo sapiens started interbreeding with Neanderthals.
“The amazing thing is that we have a good genome of a 45,000-year-old person who was close to the ancestor of all present-day humans outside Africa,” Professor Paabo said. He explained that the man lived in a time when modern humans were just about to expand out of Africa and spread into Europe and Asia.
After comparing the man’s DNA with that of people living today, the team found that the man was at a genetic mid-point between European and Asian people. This indicates that he lived close to the time before humans separated into different racial groups.
The team was also able to estimate the rate at which human DNA has changed – or mutated – over the years.
“We have caught evolution red-handed!” Professor Paabo announced.
The team found that it happened at a much slower rate than previously suggested by fossil evidence, and actually similarly to what has been observed in family generations.