So, on the planet Qualis, a reptilian species, known as the modern Qualians, evolved about 200,000 years. Before that, most fighting was down with claws and teeth, and the Qualian ancestor that had the sharpest claws was the most likely to survive and get females, and that’s how it was for thousands of years. But then the Qualians became intelligent enough to create weapons like spears and clubs, and having claws became essentially useless. But, I want to have the Qualians keep their claws still. Would it be possible for a body part which is evolutionarily outdated to remain in a species over 200,000?
Vestigiality Is Common in Evolution
People tend to talk about evolution like it is some sort of divine being who snaps his fingers and poofs away adaptations as soon as they are no longer useful or guides a species purposefully along an evolutionary path. Evolution is nothing but the most complex and far ranging game of trial and error we know of. Often times adaptations get left on vestigially. An excellent example of this can be seen in humans with their wisdom teeth and appendix. It has been ages since plant cellulose was a staple of our diet requiring an extra set of molars to masticate plant matter more thoroughly and an extra digestive enzyme chamber specialized in breaking it down. We still have both of these body parts despite the fact that they are performing no vital function and have a tendency towards contracting life threatening infections.
(Note: before anyone goes crazy in the comments about how the appendix has been theorized to act as a shelter for beneficial bacteria, this is not a vital function and one can live without with zero ill effects for their health.)
Evolution by natural selection has two main pathways, features that help a creature survive long enough to reproduce and features that are sexually selected for. (There is overlap of course, as the most commonly used example of sexually selected trait is the peacock tail which also serves to weed out those who aren't as fit due to the trade offs of the tail).
Once the best claws allowed your species to survive long enough to reproduce. Then technology came. Yet the females, on average, mate more with the males with those best claws. The survival feature becomes a display feature.
I do have to question the time frame though, how many generations is in that 200k years? Yes radical changes can happen pretty quickly under the right circumstances but overall, evolution is a slow process and is slowed further when there is less survival pressure put onto a species which the post made sound like happen when the spears were invented. (instead of 1/10 males surviving to mate, suddenly 9/10 mate, which means more potentially a population boost which weakens the selective pressure because there is just more mating happening etc)
In the old times when claws were essential hunting and fighting tools, it was obvious that strong and healthy claws were a trait which potential mates were looking for. This got so ingrained in their psychology, that they find members of their species more attractive if they have strong claws, even if they are not all that useful in modern society. Even we humans have behavioral and physical traits which we find attractive due to our hunter-gatherer origins, even though we don't live like that since many generations.
The fact that claws are no longer useful or might even be a hindrance, is not a problem. Peacocks have huge and useless tails but it's still used to select mates.
tl;dr: 200,000 is very short - it is very likely, not just possible, that there wouldn't be any changes in the appearance of your Qualians over that period.
200,000 years isn't that much in evolutionary terms. If you take a look at Wikipedia's timeline of human evolution, you can see that homo sapiens has been around for 300,000 - 800,000 years (depending on how exactly Homo heidelbergensis lineage is classified - basically if we include Neanderthals in Homo sapiens or not...). But if you look back to see when humans/pre-humans started to "lose" their large teeth, you need to go back about 3,600,000 years to Australopithecus_afarensis - that ancestor had "reduced canines and molars [compared to the modern and extinct great apes], although they are still relatively larger than in modern humans."
Note also that the same timeline states that the first evidence of "deliberately constructing stone tools" appears after the diminishing of teeth with Kenyanthropus platyops at 3,500,000 - 3,300,000 years ago.
So, you may wish to make your "modern" Qualian older than 200,000 years, but either way, it's very likely that they'll still have their sharp claws.
Traits that offer no advantage or disadvantage will persist down generations as long as there is a 50% distribution of traits between the male and female. It becomes statistically rare for a meaningless trait to disappear, because there is always a chance that either the male or female carries the trait.
Even if there are several generations that don't carry the trait. Mating with a parent who carries the trait has a 50% chance of reintroducing that trait. That trait then has to go forward many generations before it has the likelihood of being removed.
There are also cases where traits can skip generations and spontainly be re-introduced. The trait could then persist since it offers no advantage or disadvantage.
The key here is that the trait has no effect on mating. This is important, because when a trait offers neither an advantage or disadvantage it's no longer an evolutionary trait. It becomes a hereditary trait only.
Humans have many traits that have no effect on mating, and as a result they persist. We have tail bones, we have appendixes and we have remnant (a space patch of flesh from a second stomach).
There are people born without an appendix, but when they have children the trait is often re-introduced. It's why it has persisted for so long even when mutation removes it.
Because your creatures used claws as a mating advantage and they never became a disadvantage then there is no evolutionary reason for them not to persist.
The claws would be hereditary traits only but since both mating pairs have claws they forever persist down generations.
They can no more stop having claws then they can stop being replitans.
Unless something happens that changes these rules and having or not having claws changes the odds of mating. This does create some issues since claws could get in the way of tool use, but if the claws were retractable then mates with long or short claws have an equal chance of mating.
Sexual selection, as mentioned by Seserous, is probably a big part of the answer. There are also analogous situations in some human societies that might apply to an alien society. In some human cultures, long nails would get in the way of hard manual labor, be difficult to clean and probably break off. So, upper-class men, women or both would deliberately grow their nails long and manicure them to demonstrate that they had no need to do any manual labor.
Since claws are objectively useful for something, it's possible to imagine other reasons these aliens might consider it a rational sign of status. One of the simplest: brave fighters all keep their claws sharp for dueling, so a male (if their reproductive cycle is more similar to mammals’ than seahorses’) whose claws were blunt or brittle would have gotten attacked by others in prehistoric society and outcompeted. Even by the time tools and weapons could have given reptilians with broken claws a fighting chance, needing them was a sign of weakness.
Sure. 200,000 years is an eyeblink, evolutionarily.
A modern human could live in the society of our 200,000 year old ancestors. Humans have been making stone tools for 10 times that long. And like your lizardfolk, we have retained adaptations that were useful for our fierce ancestors but not so much for us. Like canine teeth.
No way to know for sure, but she is probably not going to fight anyone with those sharp little canines, or hold onto wiggling live prey she has caught with her mouth. But her ancestors surely did, much longer ago than 200,000 years.
Thinking claws specifically, consider the dewclaw. Wikipedia holds that these vestigial digits with associated claws have some use but I don't know. I have never seen a dog put them to use. The ancestral mammal that used this digit was surely millions of years ago. It takes a long time to evolve away from something useless. The get rid of it quick it has to become frankly maladaptive.
There is no reason your aliens could not have the same body plan as their ancestors of 200,000 years prior. We do.
They are Climbers
The Qualians evolved to live in a forest where the trees have broad flat trunks. Their claws let them climb sheer surfaces like a squirrel. The Qualians invented tools 200,000 years ago but were primarily hunter-gatherers until about a thousand years ago. It's only (biologically) recently they began to industrialise and chop down the trees. Until then the claws had a practical use beside sexual selection.
Other than the brilliant answers you already received, I'd like to answer to you with a question:
Why would they want to get rid of their claws at all? I mean, they're still fine natural weapons, they are useful (tooling, climbing). In fact, they can act as a deterrent when it comes to hand-to-hand fight. If both adversaries are matched in terms of natural weapons, it's unlikely they'd want to go shred each other (unless in a mind-numbing frenzy, of course, but in this case, claws are an extra, they could harm each other anyway).
It's as if we had kept our quadruman abilities and would like to get rid of them by performing foot surgery. So, hooray for natural claws!
EDIT: I can imagine someone removing their claws because they're pacifists, they actually do not like to be reminded of the brutes they used to be before civilization and prefer to artificially adapt their bodies to a condition of complete harmlessness. (this would include teeth surgeonry, acid sacs removal, etc.)
Claws aren't just for hunting and/or self-defense in a fight, you know. They can be used for hygiene too.
If claws serve to keep yourself clean, then they will be positively selected, and will tend to stay as a trait of the species.
What is the advantage of a club when you've already got sharp claws? Yes, I get that they're different and a club may be better in some cases, but just because you become intelligent, it doesn't mean you stop using your existing weapon. Beating someone with a club isn't more "intelligent" than slashing them with your claws. It may arguably be more "civilised", but civilisation at that level comes a long long time after the rise of intelligence.
I would argue that a club only becomes a better weapon when they start inventing effective defences against claw slash attacks. For example, the invention of leather armour. When you've got claws and you're faced with someone wearing claw-proof armour, what do you do? Pick up something heavy and hit them with it instead, of course. Hence the invention of the club. But the claws would still be useful against those without armour, or for finishing someone off after hitting them with a club, and as part of your own defence, so there wouldn't be any evolutionary pressure that all for them to vanish.
They still need the claws to get at their food.
It's hard to be more specific, because you give very little info about your species, but maybe they need to rip off tree bark, dig into the ground (hard clay, rocks), crack coconut-like vegetables, catch prey, climb to reach food (or other reasons), ...