It’s common knowledge that our closest living relative is the chimpanzee, with which we are thought to share around 98 percent of our DNA. Gorillas, on the other hand, are often seen as our slightly more distantly related second cousins, more brawn than brain. But male humans might actually have more in common with male gorillas than with male chimpanzees, at least in certain respects.
It turns out that the Y chromosome found within male gorillas is actually more similar to the Y chromosome found in male humans than either are to that found in male chimpanzees. This might come as somewhat of a surprise, considering that our last common ancestor with gorillas is thought to have existed around 10 million years ago, while it is thought that humans and chimps probably split as recently as 4 million years ago. Overall, however, when the rest of the genome is taken into consideration, we still come out more closely related to chimps. 
The discovery actually came about serendipitously. The researchers were initially looking at whether or not they could sequence the entire Y chromosome of a gorilla to help aid in conservation. Through genetics, those out in the field could then build up an accurate family tree of paternity, and track how males move within and between populations, which could help in the management of endangered species.
But the Y chromosome has been notoriously hard to sequence, mainly due to its small size. This is partly due to the fact that cells contain only one copy of the chromosome, meaning that it only makes up around one or two percent of the genetic information held within each cell. To get around this, the researchers were able to sort all the chromosomes based on size, increasing the amount of Y chromosome that they recovered by around 30 percent.
“Surprisingly, we found that in many ways the gorilla Y chromosome is more similar to the human Y chromosome than either is to the chimpanzee Y chromosome,” explains Kateryna Makova, one of the coauthors of the paper. “The chimpanzee Y chromosome appears to have undergone more changes in the number of genes and contains a different amount of repetitive elements compared to the human or gorilla. Moreover, a greater proportion of the gorilla Y sequences can be aligned to the human than to the chimpanzee Y chromosome.”
Basically, this means that while we are still more closely related to our chimpanzee cousins, their Y chromosome has undergone such significant change since humans and chimps split, that human Y chromosomes now more closely resemble that of gorillas. While this adds another aspect to the evolutionary relationship of the great apes, the researchers hope to be able to use this technique to help in the conservation of the apes in the wild.
Image in text: Male silverback western lowland gorilla in the Democratic Republic of Congo. GUDKOV ANDREY/Shutterstock
