There has "always" been more than one species of Homo, even at the very beginning of Homo by the way. You can't know which of them was technological. Was it rudolfensis or habilis or both. Just because Leaky says it was habilis or that they found habilis bones nearby the tools doesn't make them the makers of the "tools". They found boisei first and said the tools were made by boisei. I remember them talking about that when I was a kid. Maybe that is why I am especially skeptical of what they say actually being true. Richard also strikes me as politician with an agenda and not a good scientist. They found habilis with a slightly larger brain a few years later after boisei so now it is supposed to be a fact that habilis used tools. Rudolfensis also existed and had an even larger brain. Erectus cohabited with habilis and some now think it likely that erectus had a different ancestor like sediba so you might even have three or more lineages or species at the beginning of Homo. All three instantly elevated to the profound difference of being considered human tool users really doesn't add up. It was partially based on the opinion of someone who has a history of pushing his fossils to be human ancestors and trying to falsely attribute stone tools to his pet fossils which by the way were little more than broken rocks early on. His father even found them Calico California that were supposed to be several hundred thousand years old.
http://en.wikipedia....nthropus_boisei
That quote is to illustrate the politics that are involved and Leaky was deeply invested in Kenyan politics. They are pushing agendas and inventing narratives for fossils that don't match the evidence. The plot is flawed since it makes no biological sense that all three are going to simultaneously start using tools and occupy the same niche. The problem of not being able to identify the tool user doesn't get any better later on since there has always been multiple species of hominids at least until fairly recently. You could probably be fairly certain that neanderthals and modern humans were tool users. You could also reasonably extend that to heidelbergensis and some branch of erectus back to about 1.5 million years. That is about the time when stone hand axes started showing up. There is a problem that you can't reliably say which group of "erectus" were tool users based on fossils before a million years ago. We don't really have any idea how closely related to us some of the Asian hominids called erectus actually are. They are assumed to be erectus because of Leaky assigning erectus the narrative of being the first out of Africa and a host of other traits that are dubious at best.
It is also extremely suspect that there are multiple species that are all supposedly equally technological at the beginning. That implies that they extremely rapidly radiated into new niches but the niches were all the same which was basically a technological hominid evolving into modern humans. That seems to be the assumption that many are fine with.
The assumption is flawed that a technological hominid couldn't lose tools but it is only relevant if you can actually reliably assign tool use to them. You can't reliably do that when there are multiple species and it is a dangerous assumption to ever assume any hominid is the only one in the area. It is circular logic to assume that all hominids had tools because of that. Politics of the paleontologist cause that to happen because they want further funding and tools associated with fossils make them more valuable to museums and make it more likely they will be allowed to continue to investigate them. Even if you could reliably assign tools to them chimps also used tools so which hominids exactly are excluded from using tools. Obviously none of them are by the paleontologists except poor boisei. Mike Morwood in his book A New Human pointed out how much it damaged boisei when it was "downgraded" to just a cousin. He did everything he could to make sure that H. floresiensis was called Homo. He even has tools attributed to them that are beyond normal erectus tools even though they show signs of diverging before erectus. Some even claimed that modern humans that use the same sort of tools learned it from floresiensis. It is like they are desperate to see tool use in their pet fossils.
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From what I understand there is evidence in Israel that modern humans lived there and were replaced by neanderthals about 100,000 years ago. Then moderns apparently replaced them about 30,000 years later. That doesn't necessarily imply any attempt to interbreed. The thirty thousand years later would be about the right time for interbreeding that likely gave all non-Africans neanderthal DNA. Someone recently published a study that suggested neanderthal nuclear DNA in modern humans has been mixed up enough that it probably was introduced about that time to our species. I don't know the method they used to do that so I don't know how reliable that study is. It certainly fits the narrative of them breeding with modern humans about 60,000 to 70,000 years ago when the likely ancestors of all non-Africans left Africa. If it were a small population that first left Africa maybe 60,000 years ago then all it would take is a few successful hybrids or possibly only one to add their DNA to our species. Some of the neanderthal DNA likely would be beneficial and increase in frequency.
I think neanderthals are way too close to be the most likely ancestors of bigfoot. They certainly might have contributed genetically but there were other known populations of more primitive hominids living until at least fairly recently. I wouldn't assume we have fossil evidence of all of them. It was likely one of those more primitive groups that interbred with other hominids along the way. It seems most likely to me that they have lived in that niche for a long time. They have some features that seem distinctly different from modern humans so it would be surprising to me if it were some evolved neanderthal. We don't really know enough about neanderthals to totally discount that and evolution can certainly happen rapidly if some creature changes niche like losing technology. Some sort of punctuated equilibrium or very rapid evolution is a possibility if they are from a population that adopted a more cryptic lifestyle. That could even be accelerated by hybrids which could rapidly produce new populations. I think it is more likely that some ancient population of hominids got some more "derived" hominid's DNA possibly including us and neanderthals but didn't change form much since they didn't significantly change their niche. There is no way to really know that except possibly with DNA evidence. It would probably be very difficult to know even with DNA.