A quick look upon the world wide web will reveal people who have undergone very extreme modifications who have already morphed their bodies into their animal totems. The leopard man, the tiger woman, the zebra man and the amazing split tongue lizard man, are a few examples.
These people have chosen to morph their bodies by extreme surgery, tattoos and more.
As far as morphing with the advent of genetic manipulation, there has already been many animals with grafted cells from humans, (such as the famous mouse with a human ear on her back), but the reverse, a human with half of the human anatomy influenced by a full animal parent, is not documented.
It is certainly not beyond the realm of technology, and as to the ethical problem, a quick review of human history reveals people find rationalization for doing much worse. Shouldn't people, now aware of global warming, prepare for raising sea levels by growing gills and flippers? There are easier solutions.
People dream of flight, of being vampires and of living under the sea. Others just want to run fast, or leap high, or have the lifting strength of an ant. Could genetic manipulation, and/or evolution, provide a means to get there?
Genetics tampering is already happening on a fairly routine basis, so it would seem it is only a matter of time before people begin to start finding ways to change their human physiology. In pro athletics, for example, people have been tampering with their physical attributes and stamina for decades. Therefore, changing height, weight, proportion for extra fast, muscled, streamlined or bendable bodies is not beyond the imaginable in the near future.
However, just because something is possible does not make it wise. Social Darwinism, for example did not go well. With Eugenics, people have dreamed of editing out disease, malformation and retardation, but it is not likely to build the Utopia one might think. It is better to treat celebration of acceptance, tolerance and compassion, than to give people false hope that a better human being is in the anatomy.
It is a true lesson of factual history that people such as FDR, or Abraham Lincoln, or Winston Churchill were who are were by the very fact of what manias, depressions or physical “limitations” enabled them to be. Real human and animal strength, resilience and ability come from a host of multifactorial attributes, and none are more important than attitude and courage.
But what about evolution and morphing? That is a forever on-going process. Despite what one reads on the Internet, evolution is a factual foundation for biology. Traits are selected and reproduced over time which favor the survival of the organism. It is no different for shared traits such as flippers evolving from fore arms, or claws upon hands and feet. Evolution is the ultimate morphing mechanism. Bacteria and virus can evolve almost overnight, whereas more complex cellular structures take up to many millions of years. In the laboratory, geneticists work with insects such as fruit flies and mosquitoes, because their adaptable changes happen relatively quickly and can be manipulated. By directing and influencing what a virus can do, can have vast ramifications for humans and other animals.
Someday, there is a great chance that people will manipulate human bodies to whatever extent they can, simply because they always have. This does not mean that using animals in this way is ethical, or that results will produce favorable outcomes. In fact, once people accept that people are animals, they can begin to appreciate the marvel of bio-diversity, and accept that biomimetics will improve lives, but total morphing into other species is not necessary, as those species already have a niche, a contribution, and usually a very advanced physiology that needs no improvement. Nature is the ultimate teacher, as Einstein observed. Human beings can never catch up to nature's fifteen billion year lead in experience of creation.