Most 19th century biologists believed in orthogenesis, and they had fossil proof. Sadly, their fossil proof was because they did not believe in radioactive dating, figuring why would anyone want to date a radioactive partner? So they dated the Irish Elk fossils by the size of the antlers, assuming the oldest fossils had the smallest antlers and the most recent fossils had the largest antlers. So (they wrote) this was 'proof' that natural selection always selected for the largest antlers, until the antlers were too large making grazing and running from predators impossible, so the Irish Elk went extinct.
Actually, 19th century biologists knew that natural selection could never result in orthogenesis, they wrote 'natural selection' as weasel words because editors would not accept the correct words. Darwin said there were two kinds of selection, one was natural selection, meaning those genes that give an advantage at finding lunch and/or at not becoming someone else's lunch are slightly more likely to make it to the next generation. In one generation, there's not much difference between 99.9% likely to make it to the next generation and 99.8%, but over hundreds of generations, that 99.9% gene will get to be just about all the genes in the species. Since natural selection always selects for advantage, it can never select for antlers that are too large.
In the 20th century, the bikini came out, named after the Atoll where a lot of nuclear tests took place, so very radioactive, and the inventor said the bikini would take off like an atom bomb, so radioactive dating became fashionable, and Stephen J. Gould, who did believe in radioactive dating, proved that the largest antlers were in the middle of the range of ages of Irish Elk fossils, so no orthogenesis.
The problem with the Irish Elk is that it wasn't Irish, wasn't an Elk, and wasn't an example of orthogenesis.
Darwin always said there was another, not natural selection, and Darwin used a word that most 19th century editors rejected, but they loved 'natural selection' since that proved they were modern scientists, not fundamentalist Christians who thought the world was created, complete with fossils, in 4004 BC. The other selection comes about because most species are polygynous, meaning a very few males mate with all the females, and most males are incels. There are two ways species decide which male gets to mate with all the females in the cohort: the first, probably used by the Irish Elk, is male competition: the males duke it out, and the last male standing mates with all the females. Being able to defeat all the other males in the cohort probably means the male who fathers all the children is good at finding lunch and avoiding being lunch, so no orthogenesis.
But other species have female choice. Female fruit flies will only mate with the very best dancer, and all the males in the cohort were sons of the best dancer. Female frogs only mate with the very best singer. Some females only mate with the brightest coloured males. Since being dull and camouflaged helps with finding lunch and avoiding being lunch, getting brighter and brighter looks like it must lead to extinction from orthogenesis, but no fossil record exists that shows a progression of brighter and brighter colours leading to extinction. Orthogenesis seems very likely, but also impossible to ever find fossil proof. So 19th century biologists used the Irish Elk for their 'fossil evidence'. Which was so wrong, almost all 20th century biologists say orthogenesis is a failed theory that can never happen. And, of course, it can never happen by natural selection, and probably not when mating is decided by male competition, but it certainly looks very likely for species where the very few males who can mate are decided by female choice.
Net: from what we can see, it looks like some examples of orthogenesis must exist, but finding fossil proof can never happen.
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Since most females with no legs or with four or more legs will only mate with the male who is best at something that indicates great genes, females with exactly two legs have this as one of their mating drives. Of course, females with exactly two legs, unless they are cuckoo, desperately need a faithful partner if they are ever to become grandmothers, so one would think the desire for a faithful partner would be supreme, but Mother Nature doesn't work that way: bipedal females have at least 4 drives: 1) the attraction of a faithful mate, a drive which can be anywhere from non-existent to imperative; 2) the dislike of an unfaithful mate, again, anywhere from non-existent to overwhelming, meaning when a female discovers her mate has cheated on her, it might be anything from no problem to her feeling that she must kill one or more people; 3) the attraction of a 'hot' male, again, anywhere from non-existent to imperative; and 4) the repulsion of a male who is less than 'hot', and, again, anywhere from non-existent to imperative. So every female is completely different, so no male can understand females, and nor can females, all of whom understand themselves (maybe) but not other females, whom they assume have the same drives as they have themselves. Mother Nature experiments, trying to find the combination which provides the species with the greatest advantage for survival as a species.
While all bipedal females are different, there is an average. Examining the DNA of the pinfeathers in many, many nests, the chicks almost always have two fathers: the faithful male partner, and the 'hottest' male within flying distance of the nest. This is probably the most common bipedal female, based on my personal observation: many wives select a husband who has proven he will be faithful, will work hard to make the payments on the nest and keep worms on the table, but mating with him is an unpleasant but necessary duty; these wives then also find a really 'hot' boyfriend whom they keep absolutely secret from their faithful partner and with whom they greatly enjoy mating (and their faithful partner always gets lucky on the evening of the afternoon when she mated with her 'hot' boyfriend so he will think the chick is his own).
I spent a year sharing a 2 bedroom flat with Hank, who mated with 5 different women every day, at least 25% (and maybe more) of all the females in our village between 18 and 40, many of them married. He was incredibly something. One female told me he was not at all attractive, she hated mating with attractive males. So what it was that Hank was, I do not know, I just know it impelled a large percentage of the females in our village to mate with him.
I also spoke with Kim who begged me to listen to her, since I was the only person she could talk to. She told me she was desperate to mate, and every night went to a nightclub hoping to find someone with whom she could mate, but every nightclub had just one male and at least 20 desperate females, so she struck out 19 nights out of 20. She said she could talk to me because looking at me made her 'nauseous'. I would not have used that word, I would have said 'nauseated' but 'nauseous' is used as she used it by comedians on the Catskill circuit. She told me that, when she wants a man, she must tell him this is her first time, since men with lots of choices all want the least experienced female. Sadly, all 20 desperate females know this, so they all say, 'I've never done this kind of thing before, have you?' But it is not clear that the answer is, 'Yes, but only a time or two,' since the male they want normally has 5 different mates every day, but maybe that's what those males say. The fact that I made Kim 'nauseous' meant she would never want to mate with me, so she didn't have to lie that this was her first time, she could tell me everthing (only I said I didn't want to hear any more after she said I made her 'nauseous').
I do know (from many females complaining, and from a woman who tried unsuccessfully to derail a Supreme Court nominee) that some of these females tell the male, 'Promise me you'll never go with another woman,' and some of the males (like that Supreme Court nominee) promise, then, as soon as they finish, go looking for another, different mate. Other of these males (e.g., my flatmate) are honest, but the females who are strongly attracted to 'hot' males find their bodies cannot resist, even if their minds are appalled. Still, since the 'hot' male was honest, they don't have an intense desire for revenge.
