Just for the moment, consider the possibility that some alien visitors did a bit of tinkering with one particular group of HUMANS, say for example those who were later called the Sumerians. Why do you assume the aliens would have tinkered with chimps and gorillas, rather than actual humans?
This is actually similar to a fun little thought experiment I like to play from time to time. It doesn't really have a name, but perhaps I can dredge one up now and say it's called "From A Singularitarian Perspective".
How it works is that you have to utilize Singularitarian and rational perspectives on various theories involving the ancient alien theory, ufology, ultraterrestrial theory, and various other paranormal theories. I realized that the conspiracy theory about the Anunnaki and Illuminati, for example, is a self-constructed box that prevents much rational thought from pointing out discrepancies and logical flaws.
Let's entertain the possibility that the Anunnaki/Sumerian Gods did indeed engineer humans in ancient times. That's now a fact for the sake of this argument.
The question then is: why?
The Anunnaki theory seems, on the surface, to be sound. A very highly advanced civilization from Planet Nibiru needs gold to help save their atmosphere and prevent their own destruction after their planet collided with another. One of the planets that resulted from the impact called Earth has a lot of gold. At the time, over 400,000 years ago, Homo erectus was the most intelligent creature on Earth, closely followed by other species like Homo ergaster, Homo heidelbergensis, and Homo naledi. The Anunnaki genetically engineer various new humans out of Erectus— first the failed Neanderthals, and then the much more successful Sapiens— for the purpose of mining gold. We are essentially a slave race. When the Sumerian Gods saw their bases destroyed by climate change, they left with the intention of returning to collect their gold.
If humans were the Anunnaki, we'd probably make these same choices.
Or would we?
The problems with Zecharia Sitchin's mythology start amassing from the word go. Let's just start with Planet Nibiru: it supposedly lurks in the outer solar system, where there is no known source of solar energy to sustain life. This suggests the Anunnaki can support themselves without a star. So right off the bat, we're talking about a potentially Type 1.5 level civilization. And here comes the next major problem, this one something that Singularitarians will immediately ask: why do they need to go to Earth for gold? That's not even beginning to address why they'd need to send their own workers like Enki to mine gold— if they are capable of surviving without sunlight, that means they likely have mastered fusion and perhaps even antimatter power. In which case, such a society is certainly heavily (if not completely) automated. This is made even worse by the statement that the Anunnaki are 45 million years ahead of us.
So they're 45 million years more advanced than us, but still utilize contemporary methods of mining. We aren't even 45 million years more advanced than chimpanzees. 45 million years ago, humans were rodent-like primates.
We're expecting things such as full automation and molecular nanotechnology to come about within a century at most. To put into perspective how extreme a chance molecular nanotechnological engineering is, I came up with "atomism"— looking at Earth as a giant heap of atoms rather than a planet with complex ecosystems and finite minerals. Atomists don't mine or farm or refine or dig or anything— you get some matter and then you reorganize it into other matter. You can turn a glass of water into a bar of gold. You can turn a pile of dirt into a bar of gold. You can turn a bunch of micrometeors into a bar of gold. You can turn a heap of interstellar gas into a bar of gold. You likely get some energy out of this, something you can also use. We might have an atomist economy as soon as the 22nd century in a Singularity situation and at least some time this millennium if progress is more tempered.
45 million year-old miners, though??
Let's assume that atomism just isn't going to be a thing, then. You still have artificial intelligence + robots and mechanized factories. Even many modern mines today are highly mechanized and use few human workers. Why is 2018-era human technology superior to 45 million year old alien technology? Is it possibly because the mythology was created in the 1970s and these aliens were written as living in the year 45001970?
Why engineer Sapiens when you could build robots to do the job? The common explanation I hear from sci-fi authors why some space-faring civilizations lack robots is "they're too expensive" or "they fought a war with robots and then banned their creation." Both of which are nonsense in real life. A real robot isn't that expensive unless you're looking to create a humanoid, and that's with 2018 technology when we haven't gotten these things down to pat. In another twenty years, creating bipedal humanoids might become so simple that you could buy one at Walmart. There is more than enough material to do this, even on Earth without bringing in asteroid mining. "But their brains!" Can be controlled externally. No one said every single robot has to have its own positronic brain. Why not create one megabrain and use it to wirelessly control these robots? "That runs the risk of rebellion!" We have no way of knowing that, however. It's possible, but even if it is, it's not certain. And even if it happens once, there's nothing saying it'll always happen. You need only learn from your mistakes. If you decide your mistake was creating the thing in the first place, you'll miss out on many potential benefits.
A much more likely explanation, then, is that the Anunnaki created Sapiens as a novelty.
Of course, that's still just within the thought experiment's bounds. Outside of it, the much more likely explanation is that Sapiens evolved and certain features like webbed fingers and toes are traits found in all Homo species, but seeing as we're the only extant Homo species left, we can only see it as an oddity.