Human Digits Evolved from Fish Fins
A new study which examined existing fossil records has found that human fingers and toes did not develop in tetrapods 365 million years ago as they crawled from the sea onto land, but 380 million years ago within a species that was more like a fish. It was previously thought that as primitive tetrapods moved from water to solid ground, natural selection drove the formation of limbs.
The study, however, reveals that rudimentary fingers were already present inside the fins of the shallow-water Panderichthys, a transitional species that was nonetheless more fish than tetrapod.
"What we have shown is that the hand and the foot emerge from pre-existing bits of the fin skeleton that were just reshaped, rather than being entirely new bits that were bolted onto the existing fin skeleton,'' said co-author Per Ahlberg, a researcher at Uppsala University in Sweden.
CT scans were used to examine the minute finger rudiments that had not been examined before in existing fossils. It is hypothesized that Panderichthys developed these basic "fingers" as a support system, and not for swimming.