whale births

[Buckaroo Banzai]

Before anything I think that's good to state that i'm not a creationist or anything like that.

My question is why does most of the whales born tail first?

There's an creationist argument that assumes that if it happens, must have a reason, and they conclude that otherwise the baby whales would drown. From that they conclude that whales must have been invented rather than descend from terrestrial ancestors, because the whole first whale generation would need to know the right way to born in order to the whole new species not drown to extinction.

But that's not quite true (and the conclusions don't need any commentary), as some whales (dolphins or orcas, if I recall) are known to eventually born head-first. And grey whales generally born head first.

The best reason I can imagine for that happening is that whales have huge heads, which could be harder to be pushed out from the mother body first, whereas if the tail that is thinner comes out first, progressively expanding the aperture, the head would came out easily.

Other alternative explanation could be that somewhat "random" (random in respect with the birth position, but could have their own reasons) changes in fetal developmental patterns / uterus space that merely result in the baby whale to be in a position in which the tail is already closer to the exit when it's ready to born.

But I don't really know.

 

[Fraggle Rocker]

There's so much to learn about cetaceans. Once upon a time it was simply assumed that they were related to the other mammals they share the ocean with: pinnipeds (seals and sea lions) because that was "so obvious." How could two groups of mammals have independently adapted to marine life?

Then when I was a kid it was "known" that cetaceans had descended from bears. OK, again, this made sense. Bears are adventurous, intelligent, adaptable, and opportunistic. If a group of bears had discovered that the ocean made for an easy life, they would have stayed there. (And it does make for an easy life: warm blooded animals have a tremendous advantage over cold-blooded in the water, cf the "aquatic ape" hypothesis of human evolution.) Polar bears are already classified as "marine mammals" because they spend much of their life at sea. They're certainly good at catching fish.

Now, DNA analysis has finally established that neither is true. Of all things, whales are descended from hippopotamuses. We'll probably see Cetacea demoted to a suborder of Artiodactyla--even-toed ungulates--which includes deer, cattle, pigs, sheep, and camels.

This makes sense too. Hippos are aquatic. If a group swam (or was washed) all the way down their river into the ocean, they might have been able to adapt to feeding on krill or seaweed or even small fish. Seawater is more buoyant so they might have easily made the transition to never having to go ashore. Constant floating would have allowed them to grow much larger, rendering them invincible to all marine predators (no orcas yet!) except the biggest sharks.

They might have resolved the issue of which end to birth first before they got to the ocean. Perhaps for reasons of safety or comfort, one branch of the family began giving birth in the river instead of on shore where the predators are fiercer and the temperatures more variable.

Having established the ancestry of the whales and dolphins, the mystery is starting to evaporate, isn't it?

That's how science works.

^_^

 

[river-wind]

thanks FraggleRocker. good info