Millions of years ago our ancestors had tails. So, why don’t we?
The short answer, of course, is that we’ve lost the ability, and the need, to grow tails, thanks to evolution. The longer, more accurate, explanation is one that scientists have been trying to figure out for a long time. We might finally have an answer: genetic mutation.
In a new study, New York-based researchers theorize that a mutation, created by the addition of a short segment of DNA known as an “Alu” element, is the reason why humans and apes do not have tails, but monkeys do.
I assume that means that we’re all actually mutants – another Hollywood movie beckons!
The question of why humans lack tails has plagued Bo Xia, a NYU Grossman School of Medicine stem cell biology graduate student, since he was a child. In an effort to find some answers, Xia studied embryo development, with a particular focus on which genes were activated, and which were turned off, at different points during growth within the womb. He also analyzed tail development in other animals, and compared the DNA of tail-less apes to monkeys with tails.
Scientists have previously discovered over 30 genes responsible for tail development in various animals, including Manx cats, who famously have no tail, or a small nub for a tail. Xia theorized that the same had happened to our ancestors, and eventually, us.
The Manx cat, famous for lacking a tail, is from the Isle of Man.
A genetic mutation caused the felines to lose their tails, but some are still born with short nubs for tails, while others actually develop regular-sized tails.
Does this mean that some humans are/will be born with tails? How come we don’t hear about that?
After comparing the apes and monkeys, Xia made an exciting discovery: a mutation in the TBXT gene was evident in humans and apes but not seen in monkeys. To test the theory that this gene was the genetic mechanism responsible for tail loss in humans, Xia and his team genetically modified mice embryos to see what would happen.
They found that the addition of the TBXT gene resulted in some mice having no tails while others developed short, stubby tails.
See, there must be some humans around that have tails if our ancestors had tails. We all need to check!!!!!
This discovery led Xia and colleagues to hypothesize that 20 million years ago, a random gene mutation in an ape caused it to either develop a shortened nub of a tail, or no tail at all. That ape then passed the trait down to its offspring, and the mutation continued to make its way down several genealogies until it reached us.
Still, the question remains, why the loss of a tail was beneficial to our ancestors? Did tails get in the way more than they helped? Was there an increased risk of developing neural tube defects (NTD), which could adversely affect the brain and spine of human beings? Developing NTDs is still a concern during pregnancy, which is why the Center for Disease Control, in Atlanta, recommends “all women of reproductive age … get 400 micrograms (mcg) of folic acid every day” in an effort to prevent the defects.
Not only had I never heard of that, but I bet you didn’t know it either?
We may not yet know what the advantage was to losing our tails, but further research may one day pinpoint the answer. Or, maybe, another genetic mutation will endow future human generations with a tail once again! If our ancestors had tails, why should we be deprived!