I have heard before that inbreeding leads to genetic diversity. If this is so, why do closed groups that inbreed (dog breeds, for example) generally end up developing similar features rather than new ones?
Also, if macro-evolution is real (and desirable), why outlaw incest? And why does inbreeding only bring out select features and not introduce new ones?
Inbreeding does not lead to genetic diversity - it limits it. In a brother and sister, the data between them is very similar because they share the same parents, that is, same data source. If they were then to produce offspring, you would once again be delving into the exact same “list” of data to produce the child. Therefore your choices are limited, and when it comes to things like diseases (getting two rare pieces of data to pop up together) you are much more likely to have that happen. If the brother were to breed with someone outside his family, then that means there is a new list from which data could come from, some might be the same (e.g. both have blue eyes) but others might cancel each other out or lead to different results, thereby reducing the risk of “bad” data in the child. That’s why all golden retrievers basically look the same - inbreeding and deliberate selection of dogs with certain characteristics, but given enough time, crossbreeds between dogs would more or less all look like your typical “mutt”.
Of course, I kept saying “diseases” and “bad” things, but the same is true for good genetic traits as well. It’s just that no one ever talks about the good things! Good hair, good teeth, whatever can be selected for by breeding (as has been done with dogs) but it’s really only an issue when something bad happens - hip dysplasia in large breeds (golden retrievers), bad backs in “long” breeds (beagles and daschunds) etc.
As it’s already been pointed out, incest in fact leads to less genetic diversity. That aside, we don’t make laws according to what is genetically more advantageous. You’re confusing the term desirability in evolutionary terms with desirability in emotional terms.
Where on earth did you hear this? As has been noted, it’s completely wrong.
But no matter how much you crossbreed dogs, they will remain dogs. Just like the millions of generations they bread the fruit flies while bombarding them with radiation (which can alter the DNA). They still remained fruit flies (perhaps you would classify several new species of fruit flies that came up).
I find it interesting that you say crossbreeding generates diversity, while inbreeding does not. However, from what I have seen, it is generally accepted by evolutionists that mankind evolved from a single set of parents. And yet you have diversity. I also thought that all life is supposed to have developed from one chance combination of matter where life somehow happened. How does that jive with your comment on inbreeding?
Once again, where on earth are you getting your information about genetics and evolution from? There are so many very basic misconceptions in your last post, it will take quite some time to deal with them.
To give a very brief answer to the OP from the point of view of your second post, inbreeding WITHIN POPULATIONS decreases genetic diversity within that population. Populations are freely interbreeding units within species; interbreeding is restricted between populations (often by some geographic barrier). Isolated populations of the same species can diversify with respect to other populations if they are subject to different selective regimes and are also inbred. This process can ultimately result in different species.
Therefore inbreeding as such decreases genetic diversity. However, inbreeding in different populations can serve to fixate different genetic traits in those populations and thus differentiate them.
I think I see what the OP is trying to get at. There are two concepts that are being conflated here: genetic diversity and genetic mutations. Mutations are random changes to DNA that happen due to a number of factors and are independent of the genetic diversity of the two parents. IOW, a brother/sister pairing can produce mutations just as easily as a pairing by two distantly related individuals. It’s those mutuations that are the driving force behind evolution.
Genetic diversity is not the same as evolution. That’s just shuffling the cards in the deck-- not adding new cards. Genetic diversity helps species survive beacause the environment isn’t perfectly stable. For example, if everyone has the exact same immune system, then a new virus entering that population might wipe out everyone instead of just some fraction of the population. Or, if the species expamds into a new envirnment certain members may have a survival advantage over other members if there is diversity in that population.
And don’t be mistaken about incest. It increases the odds of congenital defects, but just by a small amount. Some people think that any offspring of an incestuous union will be some kind of deformed monster, but that simply isn’t true. While we in the US find even cousin marriages to be somewhat objectionable, in many parts of the world that is the norm-- ie, people try to keep marriages “within the family” to a certain extent.
Humans are, in fact, rather similar genetically as compared to other species. It’s generally thought that we went thru several population bottlenecks in the not-too-distant past, and that is why we seem less genetically diverse than our closest relatives-- chimps, bonobos and gorillas. But it would be a mistake to think this meant we are descended from one breeding pair-- there probably were still a few thousand individuals even in the bleakest of times.
Additionally, it’s important not to confuse the idea of Mitochondrial Eve with the idea that that female was the only breeding female of her day. She’s just the one common ancestor we all share in common-- there are still plenty of other ancestors many of us have that we don’t share in common. Just like cousins share one set of grandparents in common, they also each have a set of grandparents they don’t share in common.
It also appears that the OP might be an anti-evolutionist. I’d strongly recommend against trying to start a debate about evolution in this forum (GQ). The GD forum is better suited to that purpose and we have one of those types of debates every few months.
Macro-evolution has nothing to do with incest. Nor does it have anything to do with “desirabliity”. It’s a “big picture” view of evolution, typically focusing on aspects beyond the species level.
I would qualify this. While mutations are the raw material of evolution, saying they are the driving force gives the wrong impression. Evolution - that is, the change of gene frequencies in a population - and even speciation can occur in the absence of any mutations at all. Evolution is driven mainly by natural selection, with some contribution also due to random processes such as founder effects and genetic drift. Shuffling the deck and dealing is more important than sticking in a new card every once in a while.
Speciation, according to present thinking, is driven initially by founder effects and genetic drift in small isolated populations, followed by selection and the accumulation of novel mutations in the isolated lines.
The genetic diversity you’ve heard about is the occurance, not the number of different types of mutations. (That’s where he heard it Colibri.) The number of different mutations doesn’t increase only the chances of a mutation recuring in offspring is increased. So the number of mutations increases but the number of different mutations decreases.
You’re right, of course.
This I don’t understand, but I’ll leave that for another thread.
(I shuffled the deck a bit on your post to group the sentences more clearly for what I did and didn’t understand.)
Actually, if you go back only a few thousand years (much later than MitEve), you’ll find that every human alive today has exactly the same set of ancestors. What sets MitEve apart is that she’s the common ancestor in the entirely maternal line. That is to say, my mother’s mother’s mother’s … mother’s mother was MitEve, and yours was, too. But we almost certainly have some common ancestor who’s much closer, through a mixed line: My mother’s father’s father’s father’s mother’s father might be your father’s father’s mother’s mother’s father’s father (it might be a few more generations than that, but not all that many more).
Y-Adam is similar to MitEve, except that he’s in the male line instead of female: He’s my father’s father’s father’s … father’s father. It’s important to note that Y-Adam and MitEve were not contemporaries: The evidence is that Y-Adam lived about 60,000 - 90,000 years ago, while MitEve lived about 150,000 years ago (some anthropology student could probably get a few papers about what this difference means about male and female human sexual habits through our species’ history).
Actually, I would say macro-evolution has no scientific definition at all, as it’s a term that was coined by and is used almost exclusively by people attempting to argue that evolution doesn’t exist. I have never in my life heard a reputable scientist use the term macro-evolution. The supposed distinction between micro- and macro-evolution is completely arbitrary and has no scientific basis whatsoever.
That is entirely wrong in every particular. I can only assume you have never in your life read any textbooks or journals pertaining to evolution.
That can’t be true, although you were right in the clarification about mtDNA Eve. You’d have to go back much further than “a few” thousand years before I (of European descent) share all my ancecstors with someone who is Native American, for example. Native Americans were pretty much isolated in the Americas for 10,000 years or more. I don’t remember how the estimates work for what you’re talking about, but that would only be true (IIRC) for people living on the same continents or within the same continuously interbreeding populations.
This is the problem with debating creationists; as soon as progress starts to be made on one front, we have to fly off on a tangent.
This isn’t a problem for evolution, for a couple of reasons:
-humans were never limited to a single breeding pair; evolution happens to whole populations. Creationism typically posits descent from a single ancestral breeding pair of humans though.
-Even if you started from a single pair, diversity can arise as a result of genetic mutation. Creationism typically denies this.
So it’s actually creationism that is going to have the tough job of explaining where all this diversity came from.
Not to defend creationists, but I think you’ve mischaractarized their position. Yes, they claim descent from a single breeding pair, but most creationists recognize what they call micro-evolution: small changes within a species. What they don’t do is explain why only small changes happen or why many, many small changes can’t result in a big change.
They posit that species are fixed, and one species cannot change into another species. What they don’t realize, of course, is that the concept of a species is a human invention that only approximates the conditions in nature. That concept helps us categorize and understand the world around us, but it often obscures the interconnetiveness of all life on earth when viewed as a whole and thru the entirety of time, as opposed to what we have in front of us at this particular moment in time.
To be fair, creationism is such a broad, sprawling, inconsistent and incoherent mess, one could make pretty much any statement about it that would be denied by some and uphel;d by others.
But yes, perhaps you’re right; most creationists nowadays do seem to (sometimes grudgingly) accept what they call micro-evolution. The few I’ve spoken to support their argument of small changes within hard-limiting bounds as being caused only by recombination of existing genes.