Imagine if you could regenerate limbs that have been amputated, possibly even regrow damaged organs within your body. Well, there may have been a time long ago when your ancestors could, and the ability may be the primitive state for all four-limbed vertebrates, reports Phys.org.
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The finding comes on the heels of a new study looking at fossil amphibians, which found evidence that limb regeneration was likely an ancient feature of the common ancestor for all four-legged vertebrates — a heritage that includes humans — but that the ability was subsequently lost over the course of evolution.
Today, only salamanders have the remarkable ability to truly regenerate limbs, their tails and even organs, at least among vertebrates. Some lizards are known to be able to regrow lost tails, but they're not a perfect example.
"As opposed to lizards, which usually can only regenerate their tails once or twice and merely replace the vertebral column in the tail with a cartilaginous rod, salamanders regenerate a genuine tail including vertebral elements, the neural spine, and associated musculature," explained Dr. Constanze Bickelmann, co-author on the study.
So salamanders are unique, making them a subject of great interest to medical scientists who hope to one day discover the mechanism behind limb regeneration and perhaps apply it to human medicine. Needless to say, it is a surprise, as well as a potential boon to future medical research, to discover that salamanders may not be evolutionary oddballs at all. They may actually represent what used to be the norm for four-legged vertebrates.
"The fossil record shows that the form of limb development of modern salamanders and the high regenerative capacities are not something salamander-specific, but instead were much more wide spread and may even represent the primitive condition for all four-legged vertebrates" said Nadia Fröbisch, first author on the study. "The high regenerative capacities were lost in the evolutionary history of the different tetrapod lineages, at least once, but likely multiple times independently, among them also the lineage leading to mammals."
The study looked at fossil tetrapods (four-limbed vertebrates) from around 300 million years ago. Since this period is so close to the time when amphibians split from amniotes (reptiles, birds and mammals), looking at fossils from this period and comparing them gives a glimpse at traits that the common ancestor of both lineages likely possessed too. Sure enough, researchers found signs of limb regeneration in early organisms that represent both sides of this evolutionary split.
Right now it's unclear why salamanders retained this trait while all other tetrapods did not. But the question remains: Might there be vestigial mechanisms that all land vertebrates carry within them, that might unlock the ability anew? Such a possibility is mere speculation, but it's something that researchers will look at in future studies.
Perhaps one day we'll be able to unravel our DNA and awaken the abilities of our ancestors. Maybe we, too, will be able to regenerate lost limbs. It's certainly a more realistic possibility than it once may have seemed.