On 8/26/2013 4:07 PM, clipka wrote:
> Am 26.08.2013 23:16, schrieb Orchid Win7 v1:
>> On 26/08/2013 03:49 PM, Warp wrote:
>>> For example, all terrestrial tetrapods (which includes us) have the
>>> same basic limb bone structure: One bone (upper arm) ->  two bones
>>> (lower
>>> arm) ->  a bunch of small bones (wrist) ->  a group of long thin bones
>>> (palm/fingers).
>>
>> In a way, that's pretty amazing. But in a way, it would be far more
>> amazing if all these animals did *not* have the same bone structure -
>> that would imply a sudden change in skeletal design, which is quite
>> unlikely.
>
> You mean, like the disconnection of the collarbone from the sternum in
> felids, or the disconnection of the pelvis and complete disappearance of
> hind limbs in cetaceans?
>
In most of those cases the genes are still there, or the bones "grow 
together", such that they seem to have disappeared, but haven't, or they 
are in fact there, in some limited form, but just not obvious on first 
appearance. Deletion of entire sets of genes, for a limb, and their 
replacement with something else, instead of just adjusting the size and 
shape, doesn't happen much.

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