Humans share many characteristics with mammals. They eat, sleep, urinate, and defecate. Human females give live births to their young and produce milk to nourish them, which are the characteristics that define "mammals." Human bodies are very similar to those of chimpanzees and orangutans. Their hands look very similar and are used in similar ways. It has been found that chimpanzees make and use some tools, which suggests that humans are not distinguished by being tool-makers. Human embryos look very similar to those of animals, and they go through stages of development that appear to be replicating their stages of evolution. Geneticists have found that humans and chimpanzees share 98% or possibly 99% of the same genes.
Charles Darwin's theory of evolution has at its core the premise that all living things evolved from common ancestors. Although humans, apes, and monkeys are closer together on the evolutionary tree, humans share many things in common with even distant relatives.
1. One example is having two eyes. Many species across the planet have no eyes, and some, like spiders, have eight. Having two eyes is one trait that binds many animals together on the evolutionary tree, and serve as evidence of Darwin's theory.
2. Another example of a common ancestry is having a spinal cord. There are a wide variety of animals that have spinal cords such as fish, rabbits, and snakes. These vertebrate animals, although very different, are all distantly related to humans because of this trait.
3. An additional example of sharing a common ancestry is giving birth to live babies. While all animals reproduce in some form or another, humans share live births with animals such as dolphins, whales, giraffes, and other mammals. While other animals lay eggs, or reproduce asexually, it is giving birth to live offspring that shows that humans are bound to these other animals by a distant common ancestor.