Around 166 million years ago, the male Y chromosome started to rapidly lose genes.
"What we are left with today, after hundreds of millions of years of evolution, is a Y chromosome that has [roughly] 3% of the genes that it started with. Many scientists believe that the Y chromosome is continuing on a steady decline and will eventually lose all of its genes," explained Dr Jennifer Hughes of the Whitehead Institute for Biomedical Research.
Dr Hughes and her team investigated this theory by comparing the Y chromosome from humans with the Y chromosome from rhesus macaques. Rhesus macaques are non-human primates that share a 25 million-year-old ancestor with humans.
"By comparing the full-length Y chromosome sequences of human and rhesus macaques, we essentially have a 25 million year view back in time. We can piece together what the Y chromosome of the rhesus-human common ancestor looked like, and then figure out what happened to the Y [chromosome] along the path leading to humans over the past 25 million years," explained Dr Hughes.
If the human Y chromosome had lost genes then it would look very different to that of the rhesus macaque. What researchers found was that it looked almost identical.
"This means that the human Y [chromosome] has not been losing genes within the past 25 million years. The genes that remain on the Y [chromosome] are probably not going anywhere – they are evidently too important, which is why they have stuck around for so long," said Dr Hughes.
About the scientist: Dr Jennifer Hughes
What motivated you to become a scientist?
Science was always my favorite subject in school, and learning about evolution was so exciting to me. I loved to see connections between species and imagine how the process of natural selection shapes the diversity of life we see now.
What is the best thing about the research you do?
The best thing about research is the thrill you experience when you discover something brand new. These moments do not come often, and you usually put in countless hours of work to progress just a little bit at a time, so patience is required. I think the payoffs are well worth it though!
