This post has got me a lot of questions from creationists and junk and to be clear, Iâm totally interested in hearing their perspective on it!
The thing is though, a lot of yall are quoting scientific studies regarding inbreeding on why divergent evolution shouldnât be possible, and you should know that inbreeding and evolutionary divergence are almost completely opposite things.
INBREEDING is when there are too few individuals in a group to maintain genetic diversity. Like if only four unrelated people survived a plane crash on a deserted island. Sure, they could make two couples and have kids, and their KIDS could get together and produce grandkids, but their grandkids could produce no further generations without procreating with their own family members.
The reason procreating among family members is BAD is because like⌠if your MOM has a small chance of having kids with deformations and your DAD does too, then those chances will be doubled. Sort of. And if THAT kid has a kid with their SIBLING, whose chances are also doubled, then THEIR kid will have that same chance doubled AGAIN.
So if your parents are siblings, and your grandma and grandpa each had a 10% chance of making a baby with like. No ears, or something. Then your parents have a 20%- or 1 in 5 chance- and YOU have a 40%- or almost a 1 in 2 chance- then if YOU hook up with your sibling-cousin four generations down, you only have to have THREE KIDS, and one of them is almost guaranteed to HAVE NO EARS. And if THEY have kids with THEIR siblings? 80%. Which means 8 times out of 10 their baby wonât have ears.
And thatâs not just the ears gene compounding, thatâs EVERY GENETIC TRAIT. small nose genes will make their noses smaller and smaller until they can only breathe through the mouth. Heart conditions will compound until every birth is stillborn. The final generation will be effectively if not actually sterile. Thatâs extinction. And it almost happened to cheetahs, actually!
THAT is what compounding genomes or whatever is. Itâs interbreeding in a small group.
GENETIC DIVERGENCE is when a species is split into different groups for some reason and each group survives in different contexts long enough for them to become different species entirely, no longer able to produce fertile offspring with each other.
So like. Imagine you have a herd of sheep living on an island, yeah? And imagine the island splits in half. Both sides have a big enough population that they donât have to worry about extinction through inbreeding, but maybe the sheep on one side just HAPPEN to have more brown wool than white sheep.
Now, if one side has, say, six brown sheep and three white sheep, youâre probably going to see more brown baby sheep. Because there are more brown sheep to pass their genes on. More brown wool genes.
Now letâs say on the other island, there are six white sheep and three brown sheep. More white wool genes, so more white sheep. Maybe lighter coats until thirty years down, all of them are pale beige.
Sixty years and maybe you have an island of brown sheep and an island of white sheep.
If they can still produce fertile offspring with each other, theyâre still the same SPECIES! But maybe theyâre different BREEDS. âCause broadly speaking we kinda just made âbreedsâ up to differentiate things like that.
So how do different BREEDS become different SPECIES?
Say we still have a white sheep island and a brown sheep island. But say perhaps the white sheep island is very very hot. White fibers are hollow, so they lock in more heat, so maybe white sheep with thinner wool have an easier time cooling off. They donât die of heat so often. They retain water better. They survive to adulthood more often, so they produce offspring more often, and their offspring inherit the thinner-wool genes until another sixty years later their coats are FAR shaggier and thinner than they were originally.
And because they donât have as much padding to protect them during fights or from predators, maybe they need tougher skin. Maybe sharper hooves, bigger horns, thicker skulls. Maybe they need to be smarter or more aggressive. Sixty years, and the aggressive, shaggy, big-horned and sharp-hooved sheep survived and reproduced so well that the entire population is like that now. Maybe we start calling those goats.
And the brown sheep, maybe their island stayed cold. They kept their thick wool. But maybe when the island split, they didnât get the grassier side. Maybe they got the side with more hard, dry earth, brushy bushes, spiny trees. Food they need longer, harder, thicker teeth to chew, tougher lips to grasp, longer necks to reach. The tallest and wooliest survive, and the shorter ones donât do so well. Sixty years, and maybe theyâre all significantly woolier and bigger, with padded hoof-soles to carry the weight better and dextrous lips and tongues to manipulate their food. The ones with slightly longer guts digest food better and starve to death less often, so the gene for long digestive tracts passes on. You get something like an alpaca in this scenario, so so many generations down.
Both the alpaca-sheep and the goat-sheep are still similar, though. They both continue to eat plants. Theyâre both prey animals. They both grow long hair, and they both have two toes, and they both have wide horizontal pupils.
Now imagine a land bridge develops. These two populations can intermingle again. Do they go bag to being one big herd?
well, no. Maybe the alpacas are too tall for the goats to breed with. Maybe the goats have genes too different now, incompatible, no embryo could compute the differences.
They could still live together. They donât need to compete for the same food source anymore. The goats can live in the high cool grassy places and the alpacas can live in the brushy warmer places. Maybe they arenât aggressive towards each other, though, and travel near each other to deter predators. Or they fucking hate each other. Both could happen. This is hypothetical.
Thatâs humans and chimps. The original âsheepâ ancestor we shared is gone, but weâre still out here with varying amounts of fur and teeth, sharing our five fingers and flat tailless asses and weird spoon-shaped ears.
But yeah, no, thatâs why one species can split into two species with different genes but a small group with the SAME genes canât survive long-term.
Itâs the number of individuals, the conditions they need to survive, and how long a group is divided.
Iâm not even a scientist. I canât get into chromosomes and shit. I just think itâs neat, and itâs important, and it makes me uneasy to see people coming to me quoting studies to support theories that have no actual bearing on the things theyâre trying to prove.
My father thinks God created man. He thinks that God is infinite and uses Evolution to shape us all. I canât prove the God part and wouldnât presume to try, but the evidence for the Evolution part is far stronger than any evidence of things just suddenly appearing one day, exactly as they are right now.
And like. I canât say how God thinks. I can only see whatâs in front of me. So if my options are âpresume I know as well as God doesâ or âbelieve that in two thousand years nobody involved in translating The Bible into English has ever fucked up or mistranslated or had an ulterior motiveâ or âlisten to the story God has told with the earth around meâ, Iâm going with the third
But again. No hate. Every perspective I get the privilege of hearing is something I get to learn more about.