Charles Darwin wrote "our sympathy should be extended to all sentient beings." I agree with that idea.

Google: "A strong and rapidly growing database on animal sentience supports the acceptance of the fact that other animals are sentient beings. We know that individuals of a wide variety of species experience emotions ranging from joy and happiness to deep sadness, grief, and PTSD, along with empathy, jealousy and resentment."

A Universal Declaration on Animal Sentience.

Anyone who says that life matters less to animals than it does to us has not held in his hands an animal fighting for its life. The whole of the being of the animal is thrown into that fight, without reserve.”
-- Elisabeth Costello, in J. M. Coetzee’s The Lives of Animals

Marc Bekoff Ph.D.

This past weekend during a series of lectures I presented in Germany a number of people asked questions of the sort, "Isn't it about time we accept that animals are sentient and that we know what they want and need, and stop bickering about whether they are conscious, feel pain, and experience many different emotions?" Of course, this isn't the first time I've heard these queries, and my answer is always a resounding "Yes, we do have ample detailed scientific facts to declare that nonhuman animals are sentient beings and there are fewer and fewer skeptics."

Wikipedia - Social effects of evolutionary theory

The notion that humans share ancestors with other animals has also affected how some people view the relationship between humans and other species. Many proponents of animal rights hold that if animals and humans are of the same nature, then rights cannot be distinct to humans.

Charles Darwin, in fact, considered "sympathy" to be one of the most important moral virtues — and that it was, indeed, a product of natural selection and a trait beneficial to social animals (including humans). Darwin further argued that the most "sympathetic" societies would consequently be the most "successful." He also stated that our sympathy should be extended to "all sentient beings":

"As man advances in civilization, and small tribes are united into larger communities, the simplest reason would tell each individual that he ought to extend his social instincts and sympathies to all the members of the same nation, though personally unknown to him. This point being once reached, there is only an artificial barrier to prevent his sympathies extending to the men of all nations and races. If, indeed, such men are separated from him by great differences in appearance or habits, experience unfortunately shows us how long it is, before we look at them as our fellow-creatures. ... This virtue, one of the noblest with which man is endowed, seems to arise incidentally from our sympathies becoming more tender and more widely diffused, until they are extended to all sentient beings. As soon as this virtue is honored and practiced by some few men, it spreads through instruction and example to the young, and eventually becomes incorporated in public opinion."

— Charles Darwin; The Descent of Man, 1871