system
Given the following post, respond as if you're commenting on Reddit:
human
If evolution involves subtle changes in DNA structure, why aren't there more "transitional" species (e.g. more birds that can't really fly, or half-fish/half-land-creatures) alive today?

It seems like there would be an abundance of these transitional creatures, and the "end result" (species as we know them today) would be much smaller in comparison.

Notwithstanding fossils that may exist but we have not yet found, shouldn't we see many of these creatures living in the wild right now?  It seems like there should be *some* transitional species that, while their numbers are dwindling since they are at some sort of disadvantage, are nevertheless still around.
gpt
All the species are transitional. The word "transitional" only works retrospectively, as we normally do not know in which direction a species is evolving, and with several species to compare.


edit: 

Let's take you, and next to you your mother, and her mother and so on. If you take enough mothers, you will eventually reach a mother that looks like a small, furry animal you have never seen before. But you can see all the mothers/daughters lined up. Some have more than one child that will turn out to be different animals. Monkeys are standing closer to you, and manatees further away.

Mind that it was of course not the same individual that gave birth to different species. Imagine painting with watercolors, and from a central red you go with one brush to green and with another to blue. If the steps inbetween are as small as in evolution, you won't be able to tell them apart for a very long time.

To come back to the transitional species: each of them is - retrospectively - a transitional state. But evolution has no goal to reach, and thus no end of the transition. Yes, you are the end at the moment, but with your children, it will continue.