Has a bear ever evolved into a lion? How has an ape evolved into a human? How do species into different ‘kinds’? It is not an uncommon misconception that evolution is about the transformation of a species into a totally different species. In fact, evolution is about the accumulation of slight changes in organisms over generations.
Trust The Journey
To understand how evolution progresses let us take ageing as a metaphor.
If we go to bed as a child we wake up as a child, if we go to bed as a young woman we wake up as a young woman, if we go to bed as an elderly we wake up as an elderly. However, somehow a child grows to become a young woman, and over the years she ages and becomes an elderly. The reason for this is day-to-day ageing in humans is ever so slight that it is not meaningful to us to compare how someone looks to how someone looked the day before. However, it becomes meaningful to us only when those daily slight changes accumulate and result in a bigger change in appearance over time.
The offspring is always the the same as the species of the parents. Similar to the progress of ageing comparing the offspring to their parents is not meaningful because the evolutionary changes are ever so so light. In other words, the species of a child is always the species of the parents; lions do not give birth to bears, chimps do not give birth to humans.
It is only meaningful to do comparisons between generations when those ever so slight evolutionary changes in the species accumulate. It is needless to say, as the number of generations between the ancestor of a species and the species grows, accumulated changes grow with it too.
A Bear From A Lion
On Earth, there are no species that live alongside their ancestors. Hence the ancestor species of a contemporary species cannot be of another contemporary species. As a result, picking two extant species and asking the question if one comes from the other is not a relevant question. When it comes to comparing two extant species, what is relevant to ask is how many generations they were the same species.
A lion has never evolved into a bear, however 55 million years ago big cats and bears were the same species.
A chimp has never evolved into a human, however, 7 million years ago chimps and humans were the same species.