Special immunostaining techniques carried out by scientists from Washington's Howard University and Sorbonne University in Paris have revealed new human atavisms – remnants of anatomy that evolution never completely ditched – which help to explain how our bodies evolved.
"It used to be that we had more understanding of the early development of fishes, frogs, chicken and mice than in our own species, but these new techniques allow us to see human development in much greater detail," says Howard University evolutionary biologist, Rui Diogo.
Limb muscles thought to have been abandoned by our mammalian ancestors 250 million years ago never completely went away. In most of us, the muscles dissolve long before we're born, but these 'reptilian' remnants can still be found in some adults.
In the new study, by scanning the tissues of more than a dozen embryos and young foetuses in high-res 3D over a number of weeks, the team found tiny muscles in the hands and feet of a 7-week-old that were no longer visible by week 13.
While it's not the first time researchers have looked closely at the coming-and-going of tissues in tiny humans, most research on limb muscles has focussed on earlier weeks, missing crucial changes.
As the researchers watched, around a third of the muscles in the embryo's hands and feet simply withered away over the days, or fused with their neighbours.
Crucially, the fact some of them exist at all in our lifetime is a little surprising. Muscles called dorsometacarpales were thought to have been thrown out of the mammalian instruction manual back when evolution was still coming up with our prototypes around 250 million years ago...<<<Read The Full Article Here>>>...
