I replied with the following video explaining what micro and macroevolution really are.
Why is it inaccurate to say "macro is just lots of micro"?
Put simply, because it's more a matter of scope than scale. Macroevolution is an area of study, and what it studies is all processes that entail variations in frequencies of alleles at or above species level. We share, for example, enormous numbers of alleles with our closest primate cousins. That is, we have the exact same gene coding for the exact same protein. Every time a chimpanzee, say, or a gorilla, gives birth, this is a macroevolutionary process, because it's variation in the frequencies of those specific alleles that are carried by all three species. So macroevolution occurs with every new birth and death, and understanding the proper scope of macroevolution is a better way to counter assertions that macroevolution hasn't been observed. There really is no difference between micro and macro in this context, because they're simply different ways of looking at a single process. There is huge value in treating them as different from an epistemic perspective, because it can teach us things about evolution as a whole that might not be immediately obvious from first principles but, as with all things, the map is not the terrain. Distinguishing between them is a useful fiction; an idealisation, if you will.
) means that all objections to macroevolution evaporate, simply by being rigorous in the use of the term and reflecting its usage in the primary literature.
Problem is, macro crosses certain thresholds that are pretty much game changing.
What you see as impossibility, I see as inevitability. I think the difference in perspectives may be a problem of scale. You're looking at one individual in one generation. I'm looking at differentiating populations over millennia, where it is impossible for them to stay the same as their ancestors were. For example, whales emerged from the sister lineage of artiodactyls. Do you accept that all of these animals are biologically related to each other? Meaning that they all evolved from a common ancestor?
I don't intend to use my videos for a personalized explanation, but I did do one that covers this. So I will include it.
Evolution at every level is a matter of incremental, superficial changes being slowly compiled atop successive tiers of fundamental similarity. The adaptation you're talking about didn't begin until about the time that the cetaceans had already abandoned the land altogether.
A novel mutation will usually appear in a single individual. We don't consider it evolution unless that trait is passed through later generations until there is eventually a whole group with that modification.
Think of how dogs were derived from wolves, and how hounds were derived from dogs. We go from something like a bloodhound to something like a basset hound until we get something like a dachshund. Your question seems to be wondering why a wolf gave birth to a Weiner dog.
Remember that natural selection is based on whole populations over many generations. So we're talking about weighing population mechanics over long periods, where movement of the nostrils would be immediately advantageous, and so would tend to proliferate at the zoomed out scale.
Evolution is a theory of biodiversity. The law of biodiversity holds that one original population will become two then four, eight, sixteen and so on, except for those groups that go extinct. This is why some species that happen across a lucky improvement take quick advantage of that while others don't seem much different than their ancestors.
The same mutation isn't likely to occur independently in different lineages. That has happened, but it is extremely rare.
Different breeds of a single species can produce fertile offspring, which would often blend their differences. Different species can usually only produce infertile hybrids, and then only if they're in the same genus. Interbreeding species in different genera can't produce anything at all, even if they're both from the same taxonomic family.
They're not.
Look at the dramatic differences between skull shapes in modern dog breeds, and remember that most of that happened just within a couple thousand generations. Modern humpback whales take five to fourteen years to reach sexual maturity. The hippopotamus is the closest living relative to whales. A female hippopotamus reaches sexual maturity between five and six years old. Smaller animals tend to reach sexual maturity much faster than that. Pigs for example can reach maturity in only six months. This is what we should reasonably expect of Indohyus as well. But let's be conservative and estimate five years per generation. Indohyus dates back 50 million years. So that means ten million generations have passed since indohyus. Your question about moving the nostrils is the type of change that could happen in less than 1,000 generations, if it was something that breeders thought desirable in dogs.
It didn't. Every sibling in every generation is born with a suite of unique mutations. Humans, for example, are born with an average of 128 mutations per zygote. This is the formula for diversity. Subtle changes happen in every population. Split one population into two and even after as few as dozens of generations, we might already be able to tell the difference. If we found a lone wanderer in the no man's land between the two groups, we might be able to tell just by looking at it which group it came from, even if they were all the same group 100 generations ago.
Selective pressures apply to some environments depending on the lifestyle, the "niche". For example, sharks, dolphins, ichthyosaurs, and even some mosasaurs and crocodiles have all adopted the same shape for high speed predation in the water. Similarly, a number of different lineages have adapted the crocodile shape as an ambush predator at the water's edge. The ancestors of whales occupied that niche for a while too. So did phytosaurs and a number of giant salamanders. Eventually environmental conditions will weed out which ones were best suited for that. Crocodilians won. But there were, as I said, one lineage of crocodilians that moved to a different niche in the open ocean, developing shark-like tail flukes. Whales did the same. The difference being that whales are warm-blooded and could develop blubber, where cold waters just killed crocodiles.
Your questions are sincere. So I don't mind at all. I only suggest that we look at this scientifically, comparing two different hypotheses, biological evolution vs magical creation. Which one is born out by the evidence. Obviously creationism falls flat immediately. If you can think of another option that explains all this better than evolution, you'll be famous.
It can happen pretty quickly, when radiation or certain chemicals are involved. Or a catastrophic change in the enviroment happens.
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