Once more we delve into creationist misunderstandings of the simplest biological concepts. Honestly, I wonder about these people. It absolutely frightens me that people like this exist and can drive cars and vote.
15. Why hasn’t evolution duplicated all species on all continents?
Really? That’s a “Hard question for evolution”? My 6-year-old understands why this isn’t the case.
So, why doesn’t the Amazon rainforest have camels? This is basically what the creationist question is asking. Also, why don’t salamanders live in the Antarctic? Why don’t cheetahs live in Europe? Why are dinosaurs and other species extinct?
There’s actually two answers.
The first (and simplest) is that organisms have a niche. A niche is an ecological concept that describes both where and how an organism lives.
A habitat is where it lives. The niche includes what it eats, what eats it, what it does when resources are plentiful and what it does when resources are scarce, etc, etc, etc.
Camels, for example, are highly adapted to arid conditions. There are members of family Camelidae in South America (llamas and alpacas for example) and they are thought to have originated in North America in the Eocene.
But the camel itself (the classic bactrian or dromedary) have numerous specific adaptations for dealing with extremely arid conditions. They can lose of to 25% of their body mass due to dehydration. That loss would kill a human (and most other mammals).
Their blood cells have a different shape to withstand fast changes in the osmotic pressure when drinking huge amounts of water very quickly. A camel can drink almost a third of its body weight in water in three minutes. That would kill us by causing our blood cells to explode.
These adaptations would be completely unnecessary in the Amazon rainforest. Certainly a camel’s unique blood cell structure wouldn’t be needed in an environment with a constant water supply. A camel population would be expending a lot of energy for these adaptations. Energy that other animals wouldn’t expend. Thus the camels would be a disadvantage compared to an animal that doesn’t have those adaptations. (This is a simplistic form of what happens, but work with me here.)
This should be easy to imagine for many animals and environment combinations. Any cold-blooded species and any environment that has massive swings in temperature for example.
That’s one reason and the most obvious, the most common sense reason that all continents do not have all animal species.
The second reason is a bit more complex and it has to do with how evolution actually works.
We will never, ever see a cat evolve into a dog or a crocodile evolve into a duck. It cannot happen. If a creationist says that this is what evolution predicts, then they are fundamentally mistaken about what evolution is and how it works.
Yes, cats and dogs have a common ancestor. It was some kind of primitive carnivore (the specialized definition of having a carnasial tooth, not the ‘eats meat’ definition). That primitive carnivore had many descendants and eventually split into two (or more) populations. One population evolved over millions of years to produce the unique features in felids. Another group evolved over millions of years to produce the unique features in canids.
It’s not just about body shape or that cats (in general) have retractable claws and dogs don’t. There are thousands, if not millions, of unique genetic changes between the two major groups (canids and felids).
OK, it is theoretically possible that all of those changes could happen again over tens of millions of years to produce cats from dogs. But a pure canid will never give birth to a pure felid or even anything close. It would be a steady progression of changes in features over millions and millions of years. And, the likelihood of that happening is miniscule at best.
I’ve described this in process before and I will here again. It’s like a family tree. You and your cousin are closely related. You have the same grandfather. At this point in time, you see each other often. You and your cousin’s children play together.
A few years later, in your 40s, you move to another state for a job. Your kids may remember their cousins and you get together with everyone once every few years. But your grandchildren have never seen their (3rd, 4th?) cousins at this point. In another generation, they wouldn’t recognize any of their close relatives even if they met.
Another generation and the differences between the two groups are very different. One group has stayed in the home area, done things, established patterns of behavior. Intermarried with other local groups, etc. The other group moved to another area, done different things, established different patterns of behavior.
Maybe one group became wealthy, while the other stayed middle class. Maybe one group became poor. Maybe one group was wiped out due to low birth rates and a disease or two. Maybe one group has had high birth rates and become a leading clan in their area.
These two groups, as different as they are now, can still trace their roots back to their common ancestor.
This is an example of how speciation happens.
If you do this with animals (fruit flies, for example) in just a few generations, you have two populations that cannot interbreed. Arguably, this makes them two species. There is almost nothing you could do that could get these two unique populations back to the point where they could interbreed again.
All future populations derived from those two groups will have the unique characters from that group, but not the unique characters from the other group.
This is like you and your cousin. Let’s say your cousin inherited a widow’s peak from your grandfather. You didn’t. That’s a fairly common trait, but again, we’re using this as an example. If that trait wasn’t available in the general population, then your cousin and his lineage would be the only ones with widow’s peaks. You and your lineage wouldn’t have that trait.
Depending on the complexity of the trait, it’s possible that a single mutation could cause it, but it’s not likely that the exact same mutation will happen in the exact same place in someone else to cause the exact same trait.
Given the right conditions, we could look at a trait and say, “that person is descended from x because of that trait”. No other group has that trait.
So, that’s the reason why we’ll never have evolution produce new species that are the same as current species. The number of genes involved and the changes needed in very specific places would be highly, highly improbable. Is it theoretically possible, but in the same way that it is theoretically possible that random motion could result in all the gas molecules leaving a room and the occupants dying because of a vacuum.
The species that exist will continue to change over time.
This has taken a lot longer than I thought it would and I hope it explains everything reasonably well.
