Why do all animals have similar DNA?

Answer 1

Animals are eukaryotes with similar cells. The cells have the same kinds of organelles and the cells need the same sorts of proteins to run the cells. DNA tells how to make the proteins. It's no wonder that we have so much DNA in common.

I saw a source last week that said that people have 98-99% of their DNA in common with a chimpanzee and 60% of the DNA in common with a chicken.

Answer 2

Simple answer: radiative adaptation. This means that all animals originated from a single organism, but that the progeny of that organism specialized to fit a particular niche. Thus, all organisms come from a single ancestory, so we have the same building blocks (DNA).
Similar DNA means that animals share a lot of the same methods for life. That is, they have found a way to perform certain biochemical processes efficiently, and only those organisms who had the best means to survive did. For example, all organisms have some sort of DNA polymerase because it was the best way to synthesize new strands of DNA. The structure of polymerases is fairly generalized across the "animal" kingdom, and thus the DNA that encodes the proteins for this structure are similar.
You have to be careful when talking about animals - do you mean multicellular eukaryotes?

Answer 3

Im not sure what the question was exactly, but the DNA of all animals is made up of the same four building blocks (I cant remember from 3 years ago, but they started with A, G, C, and T, i think), and are arranged in a similar way, the double helix.

Answer 4

the theory is that all living things have DNA saying that they all came from a common ancestor, then branching into diffent organisms.

Answer 5

They all shared the same ancestor, in Cambrian period, 370million years ago (app) an animal named PIKAIA.