WASHINGTON — Tails were once a feature of our ancient animal ancestors. Why did they disappear?
Around 20 to 25 million years ago, during the split between apes and monkeys, the evolutionary branches of our family tree shed their tails. Scientists have been puzzled about the reasons behind this change since the time of Darwin.
Now, a group of researchers has pinpointed at least one crucial genetic mutation that played a role in this transformation.
“We identified a single mutation in a highly important gene,” explained Beau Xia, a geneticist at the Broad Institute and one of the authors of the study that was recently published in Nature magazine.
By comparing the genetic makeup of six types of great apes, including humans, and 15 species of tailed monkeys, researchers found significant genetic differences between the two groups. To test their hypothesis, they used the gene-editing tool CRISPR to alter the same genetic spot in mouse embryos, leading to the birth of tailless mice.
Xia cautioned that there may be other genetic factors contributing to the loss of tails.
An intriguing aspect of this evolutionary change is whether the absence of tails conferred an advantage to our ape ancestors and ultimately to humans. Was it a random mutation or did it serve a purpose in survival?
“It could have been purely coincidental, but it may have provided a significant evolutionary benefit,” suggested Miriam Konkel, an evolutionary geneticist at Clemson University who was not part of the study.
Various theories speculate on the advantages of being tailless. Some suggest that it may be linked to the development of upright walking in humans.
Rick Potts, who leads the Human Origins Project at the Smithsonian Institution and was not involved in this study, believes that the absence of tails in some apes could be due to their vertical posture even when still in trees. This transition might have been the initial step.
Although not all great apes are land dwellers, orangutans and gibbons are examples of tailless apes that continue to live in trees. Their movements differ significantly from monkeys, as they do not need tails for balance while moving among branches.
Study co-author Itai Yanai, a biologist at New York University, acknowledges that losing the tail was a major change. However, the true reasons behind it remain a mystery that can only be unraveled with a time machine.
Source: www.nbcnews.com
