The fossils of Cro-Magnon were found in

Gill clefts and notochord appear in the embryonic development of all vertebrates from fishes to mammals. This supports the theory of

There are how many total races of man

The theory of random genetic drift was proposed by

Contribution of scientist : August Weismann

In the developmental history of mammalian heart, it is observed that it passes through a two-chambered fish-like heart, three-chambered frog-like heart and finally four-chambered stage. To which hypothesis can this above cited statement be approximated