Would you care to start a thread and present evidence for a unbroken line of modern mankind and modern horse kind to back up this assertion.
Why would we need to? They are both in the mammal kind.
Does Science says all life has a common ancestor?
The Bible says all kinds came from one single ancestor that gave them life.
In fact the Bible said it at least 3,000 years before science did.
Science does not say that all life has a common ancestor. The evidence says this, and this evidence has been around since the beginning of life, 3.5 billion years before the Bible was written.
You also forget that the map is not the territory. The menu is not the meal. A book can claim that the Earth is a cube, but the Earth will not transform into a cube upon reading the book. There is this thing out there called reality, and it describes itself.
So in reality, where do we find these divisions in kinds? Anywhere? For example, what genetic markers should not be shared by species from different kinds, and why? What mixtures of characteristics should we not see in living and fossil species, and why? If you can't explain these things then you have no way of knowing if two species belong to the same kind or not.
™ Version 4.2
