Question: Why do scientists think that human beings are apart of an Evelution from animal to man.

Miriam Hogg answered on 29 Jun 2020:

So the best way to think about evolution is not that one animal turns into another, its more that a species of animal will split and one part will evolve in one way and the other will evolve another way depending on thier surroundings.
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So there are a few different reasons why scientists think humans and animals evolve.
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Firstly we have fossils from different times in history showing how animals like crocodiles changed over millions of years. So by comparing the fossils over time we can see changes in jaw size, arm and body length for exanple. We can do this for lots of animals, including humans. Skulls of our species over time has changed in size and shape as well as body structure. So we know that animals change over time.
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Second is our DNA. Our DNA is like a book of everything we need to make a human. Some parts of that book are the same for lots of animals because we are related to them distantly. We share 97% of our DNA with Apes so we know we are closely related and at some point in the far past we were the same species and one group split off and evolved differently to the other group and became us. We share certain parts of our DNA with nearly every animal so we know that we had common species millions of years ago.
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Thirdly we can see evolution happening! When Charles Darwin was fist found this idea he studied the same bird that lived on different islands and saw that, although they were the same species, they had different shaped beaks and differet body sizes. If those birds stayed on those islands long enough they would probably become completely different species eventually! You can also see how dogs have changed over time, if you look at pictures from the Victorian times of certain dog breeds and compare them to now you can see how they have changed in a few hundred years! (humans have selectively bred dogs so they have changed more rapidly than they would naturally) so if we can force dogs to change that much in a relatively small amount of time, imagine how millions of years can change animals!
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So we can think about something like fish. We have a big tank of fish and find one of the fish is much faster than the others, so split the tank into two with the fast fish in one. That fish would probably have babies who are also fast who would also have babies who are fast and so on. eventually the tank with one original fast fish would be full of fast fish. While the other tank would have normal speed fish. If you have two tanks of fish and let them evolve for thousands of years with these different random helpful and non helpful traits eventually the two tanks would become different species. Thats what has happened on a large scale with the whole world!