This scenario teeters on the verge of B-movie science fiction, but still, let's say that some ambitious scientist, who is an avid fan of mythology, uses that childhood obsession to test genetic experiments on his fellow human. The list is as follows:


A population of humans where 20% of their genetic makeup stems from Capra sibirica, the Siberian Ibex.


A population of humans where 20% of their genetic makeup stems from Panthera pardus, the Leopard.


A population of humans where 20% of their genetic makeup stems from Canis lupus, the Grey Wolf.


A population of humans where 20% of their genetic makeup stems from either Zalophus californianus, the California Sea Lion, or Eumetopias jubatus, Stellar's Sea Lion.


A population of humans where 20% of their genetic makeup stems from Tursiops truncatus, the Bottlenose Dolphin.


A population of humans where 20% of their genetic makeup stems from either Ursus maritimus, the Polar Bear, or Ursus arctos, the Brown Bear.

Note that the one theme of this list is that the human genome has been altered by 20% to create these mythological hybrids. Is that percentage major enough for changes in physical exterior characteristics? Would behavior be affected?

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    $\begingroup$ The difference between different animals (even different mammals) is sufficient to make a random 20% shift from one animal towards another unlikely to survive. Different mammals don't have the same number of chromosomes so it is unclear what 20% would be replaced with. A stretch of human DNA doesn't necessarily have an analogue in another mammal. It might help to edit the question to describe the outcome you're hoping for, rather than fixing 20%, or else clarify why it needs to be 20% if that happens to be part of your plot $\endgroup$ – trichoplax Oct 7 '15 at 11:49
  • $\begingroup$ So the question is; Given a 20 percent change in genetic structure how much change could you see in a hybrid species? $\endgroup$ – James Oct 7 '15 at 13:37

What JustAnother means to say, is that we are already much more closely related (genetically) to the mammals you listed, than you previously would have expected. The human and bear genomes are very much similar and the difference between them is far lesser than you would expect.

You can read about the comparison of human and other creatures genomes on this site and also on this site.

Now back to your question. As for creating semi-human-semi-beast hybrids, the choice is entirely yours. If, instead of mixing human genomes with other mammals, you instead go on and change the human genome in a way that modifies them to your desired result. That is how evolution works, too.

For example, lets say we want to create a werewolf. We begin with a human genome. We change the genes controlling the shape of the head. This will involve changing the shapes of some 16 or so bones including jawbone, several skull bones, the position of the gap where spinal cord attaches to the brain, the nose bones, the nasal cavity, the ear structure and the neck. We can then choose whether we want human hair type or wolf hair. Also the concentration of the hair. After we are done with this, we have successfully created a werewolf-looking creature.

But what defines a werewolf? Is it looks only? What does a werewolf eat? What is its general psychology? The language? The emotions? That is for you to decide. Although changing the shape of the skull will definitely have some impact on the brain shape (if not the size too), the configuration of the brain parts (cerebrum, cerebellum, medulla etc) depends solely on you. The way you changed its genome to modify it's physical structure, so you can to change its behavior according to your needs. If you want to make him a carnivore, you should consider changing his teeth type, make some modifications to his digestive system, perhaps make him more instinct-oriented (animals) than logic-oriented (human).

All in all, it's your pick. You can have a very friendly and docile vegetarian werewolf if you want. And a very menacing and horrible, monstrous satyr if you so choose. It is not a question to ask how the behavior would change, it is upto you to decide how you want to change it.

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We would be essentially weirdly enough, more Human and less everything else in these scenarios, well at least based on the findings presented in this article. Humans currently do share high percentages of our DNA with other animals, if humans were to share so little DNA with these lifeforms it is unimaginable what we would look like. The average human shares 60% of our DNA with the common fruit fly so being 3x more isolated from such a generic creature would mean that humans would be separated from mammals, reptiles, insects, and would possibly be the most alien life form to inhabit Earth (we are talking B-grade movie here!).

This would definitely have an impact on the behavior of humans as you could twist it anyway you would like. Being only 20% related to Dolphins could mean that humans are more similar to plants. Who knows, maybe instead of hunting for squids in the ocean, they will stand in the sea and convert water into hydrogen for consumption and oxygen as exhaust. The possibilities are endless!

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