Every whale and dolphin evolved from a deer-like animal with slender, hoofed legs,
which lived between 53 and 56 million years ago. Over time, these
ancestral creatures became more streamlined, and their tails widened
into flukes. They lost their hind limbs, and their front ones became
paddles. And they became smarter. Today, whales and dolphins –
collectively known as cetaceans – are among the most intelligent of
mammals, with smarts that rival our own primate relatives.
Now, Shixia Xu from Nanjing Normal University has found that a gene
called ASPM seems to have played an important role in the evolution of
cetacean brains. The gene shows clear signatures of adaptive change at
two points in history, when the brains of some cetaceans ballooned in
size. But ASPM has also been linked to the evolution of bigger brains in
another branch of the mammal family tree – ours. It went through similar bursts of accelerated evolution in the great apes, and especially in our own ancestors after they split away from chimpanzees.
It seems that both primates and cetaceans—the intellectual
heavyweights of the animal world—could owe our bulging brains to changes
in the same gene. “It’s a significant result,” says Michael McGowen,
who studies the genetic evolution of whales at Wayne State University.
“The work on ASPM shows clear evidence of adaptive evolution, and adds
to the growing evidence of convergence between primates and cetaceans
from a molecular perspective.”
… continue reading at Not Exactly Rocket Science.
Note: it is one of the microcephalin genes, if you wondered.