In a recent biological study published in the journal Development, scientists have found that fetuses are equipped with extra, lizard-like hand muscles that date back nearly 250 million years. It is believed that these muscles are evolutionary left-overs from when reptiles were slowly transitioning to what we now know as mammals. These muscles will, however, disappear throughout the development of the fetus.
While most babies will lose these extra muscles prior to birth, biologists aren't exactly sure why humans even continue to develop them at all. Albeit, some humans are in fact born with extra muscles in their hands, it is extremely rare for all of these dorsometacarpales to remain. In cases of extra hand muscles remaining there is typically some type of limb deformity. The researchers hope to use this recent discovery to better understand similar birth defects.
On the other hand, biologists believe that these disappearing muscles are a significant step in the evolutionary process that allowed humans to have opposable, dexterous thumbs. Our thumbs contain one extra muscle more than that found in our fingers.
Lead author on the study, Dr. Rui Diogo, said: "We have a lot of muscles going to the thumb, very precise thumb movements, but we lost a lot of muscles that are going to the other digits."
"In our evolution, we do not need them so much," he explains to the BBC. "Why are they there? Probably, we cannot just say in evolution, 'Look, I will delete from scratch, from day zero, the muscle going to digits two, three, four, five and I will just keep the one going to the thumb.'"
Of course, most of us are familiar with our typically "unnecessary" body parts, such as the appendix or the wisdom teeth, but Dr. Diogo considers these evolutionary remnants in particular, to be far more intriguing.
"These muscles were lost 250 million years ago," Dr. Diogo said. "No adult mammal, no rat, no dog has those muscles. It's impressive. It was really a long time ago."
The recent discovery has conjured up a great deal of questions. Dr. Sergio Almécija, for example, an anthropologist who studies ape and human evolution, wonders what else humans are losing during this period, and also what else might be discovered as more in-depth studies are conducted. And most importantly, Dr. Almécija asks why these attributes are created and then subsequently erased.
While the primate species seem to retain these extra muscles, which can also be found in the feet of babies still in the womb, we adult humans for some reason have lost the need.
Some biologists, however, do not consider this as an improvement in the human species. Instead, it is believed that it could actually be a missing piece that would create super humans. This comes from the assumption that humans would then have the ability to move all digits, even our feet, as thumbs.
