Evidences for MACROevolution

Manatees having hipsockets! As well as their having elephant-like toenails and flipper skeletons homologous to the forelimbs of terrestrial tetrapods, having 1 upper arm bone, 2 forearm bones, and cluster of wrist bones, and finger bones. Plus our having found a fossil of a manatee ancestor (evident from its downturned jaw, solid ribs, and other characters) that had 4 full-size legs, and then finding a more-recent one that had 4 legs but with the back 2 reduced in size.

Whales and dolphin embryos beginning to form hind limbs! Plus their forming a full coat of hair, just to lose it before birth. And they don’t form their blowholes directly: instead, they first form 2 nostrils just above the mouth – like 4-legged land mammals have – that then must migrate to the top of the head and fuse in order to form the blowhole. Then there are the fossils of half a dozen fossil species with transitional features.

Birds having some genes for making teeth! These are remnant genetic instructions, left over from the reptilian ancestors. So too are the genetic instructions that make birds embryos first form a long, bony tail - no birds have long bony tails, but reptiles do - just to have a good part of it resorbed and fused to form the avian pygostyle. Then there's the Hoatzin having claws in its front limbs for a short while after being born: birds don't have claws on their front limbs, but reptiles do. Then there's Archaeopteryx: a fossil "bird" (it had feathers, wings, and a furcula) that had a set of reptilian characters, such as teeth, claws on the front limbs, a long bony tail, and a neck that attaches to the back of the skull ... no modern birds have those 4 characters, but modern reptiles do. We also have found fossils that show many extinct reptiles - dinosaurs - had feathers, ranging from extremely simple to complex. And reptiles and birds group together, at the exclusion of all other animals, because they express beta-keratins in the skin. And, the beta-keratin in the claws of the alligator (a reptile) and the beta-keratin of the feathers of birds have a core box that shows 80% (IIRC) sequence identity. We've also found a very strong link between birds and reptiles in their lungs: for a long time, a unidirectional flow of air through the lungs was considered a character unique to birds: all birds had it, and no animals other than birds had it. But a recent study found that a reptile - the alligator - also has unidirectional flow of air through its lung! Further, we have found fossils of extinct reptiles - dinosaurs - that show they have unidirectional flow of air through the lungs, with accessory air sacs, that protruded into partially hollowed-out bones. And the old problem about digit identity has been solved by embryonic studies, which showed that a shift in Hox gene expression transformed the digit identities.

Human embryos forming a postanal tail! Unlike the vast vast majority of vertebrates, humans don't have tails (and neither do chimps, bonobos, gorillas, or orangutans, our 4 closest living relatives!), yet we form one in embryonic development, just to have it largely resorbed and fused to form our coccyx. Human embryos also start off with a very fishlike arrangement of aortae, arteries, and aortic arches, which then require much remodeling to arrive at an arrangement appropriate for humans. Also, human embryos form fishlike pharyngeal arches, and even, transiently, pharyngeal slits.

Then there's genetic evidence all over the place.

For example, fruit flies have a series of genes called Hox gene along a chromosome that helps pattern their anterioposterior axis during development, with the linear location of the genes along the chromosome matching the linear body portions that they affect. Turns out that mice and humans and fish also have Hox genes, arranged in the order along chromosomes that corresponds to the region of the embryo they affect.

Then there is the master control gene for eye development, Pax6. Fruit flies have a copy (called eyeless, because it was named before it was realized that it was the same gene named Pax6 in other organisms) that can be replaced with the mouse Pax6, and it works! Pax6 kicks off eye development in animals as different as humans, mice, squid, and fruit flies.

Then there is the shared embryonic process of tetrapod limb development. Whether a tetrapod is a human, mouse, chicken, or whatever, the same general process occurs (an AER is formed that reciprocally induces the underlying mesoderm, and a ZPA is formed which produces shh (sonic hedgehog), and RA (retinoic acid) has the same effect, the 5' Hox genes play a role in patterning the limbs, etc.).

The really interesting thing is that the above shared developmental pathway for tetrapod limbs is also shared by fish! So it's not just the fossil record we have showing paired fish fins evolving into tetrapod limbs, we also have the underlying genetic similarities s