Evolution of whales

[Uphill Battle]

Anyone care to explain the evolution of the whale? Just out of curiosity, I want to know what the theory of how a mammal became a waterbound creature.

Did a land creature decide to return to the sea?

Or did a fish creature evolve into a mammal?

what theories are there for this?

 

[Tomk80]

Land creatures started occupying a niche in the sea.

 

[Uphill Battle]

how exactly? At what point did not having legs become beneficial?

 

[ChrisS]

This is something I've been wondering as well. Though I'm sure there are numerous explanations for this. According to evolutionary laws though, I believe that the whale needs a common ancestor from the land.

Wouldn't a fish evolving into a mammal go against evolutionary theory? Unless the mammal became the ancestor of all other mammals.

 

[Tomk80]

This is something I've been wondering as well. Though I'm sure there are numerous explanations for this. According to evolutionary laws though, I believe that the whale need a common ancestor from the land.

Wouldn't a fish evolving into a mammal go against evolutionary theory? Unless the mammal became the ancestor of all other mammals.

Indeed, fish evolving into whales would be very contradictory to the theory of evolution. There really isn't a good logical pathway on how this would occur. So whales evolved from land-based mammals.

Of course those land-based mammals evolved from reptiles, which evolved from amphibians, which evolved from fish. So basically, we could say that fish followed a little detour here But fish evolving directly into whales, nope, didn't happen. At least not according to the theory of evolution.

 

[Uphill Battle]

Ok, but what about the steps required? Going from a quadropedal land animal to a whale, would take more than just minor changes, it's a complete overhaul. At what point do the legs fuse to a single rear fin? At what point does the spinal column go from having the legs hinged perpendicular to what you observe in a whale today, with the horizontal tail, in line with the spine?

 

[Freodin]

Anyone care to explain the evolution of the whale? Just out of curiosity, I want to know what the theory of how a mammal became a waterbound creature.

Did a land creature decide to return to the sea?

Or did a fish creature evolve into a mammal?

what theories are there for this?

Language! Take care of your language!

Current theory on this is that whales are indeed descendents of land-dwelling mammals - but there was no "decision" to "return to the sea". This mammal (ask someone else for specifics) occupied a niche that lead it to rely more and more on the water as the element of living.

Biologically unrelated (or rather - not very closely related) examples would be otters. River otters spend a lot of time in the water, sea otters live almost exclusively in the water. In a few million years, the descendents of modern otters might have lost their legs, and became another species of water-dwelling mammals. Seals and their cousin kinds might have already started on this route.

 

[Late_Cretaceous]

There are numerous mammals that are transitional between aquatic and terrestrial habitats. This list shows that transitional semi aquatic mammals with legs that are less then ideal for life on land are not only possible, but can be seen today.

Polar bears - fully functional legs for land, but excellent swimmers who can spend hours upon hours swimming in deep water.
Hippos - fully functional legs for land, but spend much of their time partially submerged in shallow water

Otters- not quite as good on land as terrestrial animals, probably more comfortable/efficient in water where they spend most of their time.

Walruses and seals - a range of species that have legs that are very inefficient or even totally useless on land. Their legs make excellent flippers for swimming, and could almost be regarded as fins. Some spend most of their lives in the water comming to shore only for breeding (some even mate at sea).

Whales and dophins. Totally aquatic, even giving birth in the water. Legs are totally transformed to fins.


The earliest whales were somewhat like otters with large heads. It is believed they ambushed their prey from the waters edge in a way similar to crocodiles.

 

[Linux98]

The earliest whales were somewhat like otters with large heads. It is believed they ambushed their prey from the waters edge in a way similar to crocodiles.

LOL...how do you know this? Where are the fossils of the pre-whale/otter and what is the evidence for the shore ambush tactics?

 

[Split Rock]

Ok, but what about the steps required? Going from a quadropedal land animal to a whale, would take more than just minor changes, it's a complete overhaul. At what point do the legs fuse to a single rear fin? At what point does the spinal column go from having the legs hinged perpendicular to what you observe in a whale today, with the horizontal tail, in line with the spine?

The fluke at the end of a whale's tail is entirely derived from the tail, not from fused legs. The rear legs were lost, though not entirely; whales have remnants of leg bones in their body, as well as a pelvis. In fact, some whales have been found with little functional rear legs, which indicate that whales have the genetic information to create rear legs (these are called atavisms or "throwbacks") See: http://www.edwardtbabinski.us/babinski/whale_evolution.html

In addition, whale embryos form leg buds during development which are quickly reabsorbed. These leg buds develop into rear legs in other mammals. See: http://darla.neoucom.edu/DLDD/

Third, we have found whale intermediates in the fossil record that have small rear legs, such as Durodon and Basilosaurous. Earlier in the record we have found whale like animals with four normal proportioned legs. see: http://www-personal.umich.edu/~gingeric/PDGwhales/Whales.htm

Taken all together, these are rather bizarre findings that are difficult to explain with a model in which whales were designed to be aquatic from the beginning. In light of evolution, however, they all make sense.

 

[Late_Cretaceous]

LOL...how do you know this? Where are the fossils of the pre-whale/otter and what is the evidence for the shore ambush tactics?

From fossils of primitive whales, of which there are several. One in particular called ambulocetus

An animal's lifestlyle can be infered from it's body plan. With the large head and short lets and sharp teeth - it is quite similar to a crocodile so we can infer that it may have fed like one. Of course we don't know for sure, but it would be unlikely that this animal couuld have fed like a gazelle or a cheetah.

PWN3D

 

[Karl - Liberal Backslider]

LOL...how do you know this? Where are the fossils of the pre-whale/otter and what is the evidence for the shore ambush tactics?

In my avatar. That is a reconstruction of one of the animals in question, called Ambulocetus natans.

Can I clear something else up? The rear legs did not fuse into the tail flukes. The rear legs were gradually lost (Google Basilosaurus). The tail is descended from the tail of the land dwelling ancestors. The up and down motion is not however analogous with the wagging of the tail; it is an extension of the spinal flexion seen when land animals run.

 

[nvxplorer]

Taken all together, these are rather bizarre findings that are difficult to explain with a model in which whales were designed to be aquatic from the beginning. In light of evolution, however, they all make sense.

Agreed. The whale is perhaps the best argument against design. A designer who obviously had knowlege of gills would not design a completely aquatic animal with lungs.

 

[Uphill Battle]

From fossils of primitive whales, of which there are several. One in particular called ambulocetus

An animal's lifestlyle can be infered from it's body plan. With the large head and short lets and sharp teeth - it is quite similar to a crocodile so we can infer that it may have fed like one. Of course we don't know for sure, but it would be unlikely that this animal couuld have fed like a gazelle or a cheetah.

PWN3D

care to tell me which bones were the found ones... the shaded or the non shaded?

 

[Uphill Battle]

Agreed. The whale is perhaps the best argument against design. A designer who obviously had knowlege of gills would not design a completely aquatic animal with lungs.

or, perhaps, an arguement against natural selection, as I see no benifit to go from air breating on land to air breating in the sea.

 

[Late_Cretaceous]

In that one particular example, shaded. And there are other specimins as well.

 

[Late_Cretaceous]

as I see no benifit to go from air breating on land to air breating in the sea.

The marine environment is a more stable environement then the land. No droughts or floods you see. Food sources are abundant and reliable. There is lots of evolutionary pressure (or opportunity) for terrestrial organisms to venture to the sea.

 

[Uphill Battle]

ah, I see. They "extrapolated" quite a bit on the skeletal structure on that one, it would seem.

 

[Uphill Battle]

The marine environment is a more stable environement then the land. No droughts or floods you see. Food sources are abundant and reliable. There is lots of evolutionary pressure (or opportunity) for terrestrial organisms to venture to the sea.

sure, but then why not evolve gills? it would be a benefit, would it not?

 

[Tomk80]

sure, but then why not evolve gills? it would be a benefit, would it not?

Because gills require a completely different circulatory system. Evolution does not go the way of the most efficient, it goes with what works good enough given what it has. Evolution cannot plan ahead and decide that gills were beneficial.