Horse, Deer, Elephant and Moose

[dulsi]

When Thyfur did the Zebra and others I noticed the increased cost for hands and biped. I knew that in TMNT some creatures used more BIO-E to get human features than others. I assumed that was to keep the characters roughly human sized because it was done on large creatures. However, AtB2 tries to let you play the large animals without sacrificing size levels for BIO-E if you want.

So why do Horse and Deer cost more BIO-E to have hands and biped? If it is just how much evolution is needed shouldn't Goat and Cattle have similar changes? Is it really that much easier for an Aligator, Horse, or Elephant to get human looks than a Moose?