That puts the legend back in time to 30,000 years ago, or more.
Actually, I'd say it puts it back to X? years ago. I am skeptical about both Usher's 4000 year chronology and the chronology of modern science. I believe the scriptures to be inerrant IN THE ORIGINAL MANUSCRIPTS. However, when you consider how much language can change over the course of thousands of years, and also realize that Hebrew didn't use numbers, but letters of their alphabet, then the possibility has to be kept open that the text we have now in Genesis listing the ages of the patriarchs might not mean the same thing it did when written. That's not saying the Bible is in error, it is just leaving open the possibility that our interpretation of it is. As for science, they operate on a premise of uniformity of natural causes in a closed system. As a Bible-believing Christian, I operate on a premise of uniformity of natural causes within an OPEN system, subject to intervention by Divine creation and providence. In particular, the Bible tells us that there have been three global/universal discontinuities in the uniformity of natural causes due to divine intervention: the creation itself, the fall, and the flood. I would argue that we cannot know with any certainty that everything in the world before the flood was just as it is now after the flood. The earth's orbit and rotation could have been different, the occurance of C14 and other radioisotopes could be different, lots of things could be different. The chronology for natural history and anthropology that scientists have constructed take no accout of this, and thus their chronology must be suspect.
I have no problem with the idea of antediluvian patriarchs and neanderthals being contemporaneous. I just can't assign a particular date to them with any degree of confidence.
By the way, I also don't have any problem with the idea of a neolithic culture of antediluvian patriarchs coexisting with populations of paleolithic neanderthals and paleolithic homo sapiens sapiens. Such a neolithic culture could have been a very small part of the total antediluvian population, and finding any evidence that might have survived the flood could be like searching for a needle in a haystack. Nor do I have any problem with the idea that humankind may have been created civilized but then that large portions rapidly regressed to a more primitative state. Such cultural regressions are fairly common and well documented by anthropologists. It is only those who vainly believe in the inevitable progress of humanity as the hope of their salvation who are uncomfortable talking about that fact.