One could just as easily define the different "races" of humanity as different "species"; it is an arbitrary term, the definition of which depends entirely on the assumptions and definitions that one starts out with in the first place. That's why evolutionary physchology is a more useful discipline for understanding the differences between human populations, because it takes into account the behaviours and group strategies that differentiate different human evolutionary groups, rather than obsessing over just the bare physical differnences between groups.
My own best guess as to the reality of the situation is that modern humans were somehow genetically re-engineered from neanderthals via some process which took no more than a few generations. Gunnar Heinsohn of the University of Bremen has noted that no realistic interpretation of stratigraphic evidence would assign any more than a couple of generations to the changeover from neanderthal to modern man:
Mueller-Karpe, the first name in continental paleoanthropology, wrote thirty years ago on the two strata of homo erectus at Swanscombe/England: "A difference between the tools in the upper and in the lower stratum is not recognizable. (From a geological point of view it is uncertain if between the two strata there passed decades, centuries or millennia.)" (Handbuch der Vorgeschichte, Vol I, Munich 1966, p. 293).The outstanding scholar never returned to this hint that in reality there may have passed ten years where the textbooks enlist one thousand years. Yet, I tried to follow this thread. I went to the stratigraphies of the Old Stone Age which usually look as follows
modern man (homo sapiens sapiens)
Neanderthal man (homo sapiens neanderthalensis)
Homo erectus (invents fire and is considered the first intelligent man).
In my book "Wie alt ist das Menschengeschlecht?" [How Ancient is Man?], 1996, 2nd edition, I focused for Neanderthal man on his best preserved stratigraphy: Combe Grenal in France. Within 4 m of debris it exhibited 55 strata dated conventionally between -90,000 and -30,000. Roughly one millennium was thus assigned to some 7 cm of debris per stratum. Close scrutiny had revealed that most strata were only used in the summer. Thus, ca. one thousand summers were assigned to each stratum. If, however, the site lay idle in winter and spring one would have expected substratification. Ideally, one would look for one thousand substrata for the one thousand summers. Yet, not even two substrata were discovered in any of the strata. They themselves were the substrata in the 4 m stratigraphy. They, thus, were not good for 60,000 but only for 55 years.
I tested this assumption with the tool count. According to the Binfords' research--done on North American Indians--each tribal adult has at least five tool kits with some eight tools in each of them. At every time 800 tools existed in a band of 20 adults. Assuming that each tool lasted an entire generation (15 female years), Combe Grenals 4,000 generations in 60,000 years should have produced some 3.2 million tools. By going closer to the actual life time of flint tools tens of millions of tools would have to be expected for Combe Grenal. Ony 19,000 (nineteen thousand) remains of tools, however, were found by the excavators.
There seems to be no way out but to cut down the age of Neanderthal man at Combe Grenal from some 60,000 to some 60 years.
I applied the stratigraphical approach to the best caves in Europe for the entire time from Erectus to the Iron Age and reached at the following tentative chronology for intelligent man:
-600 onwards Iron Age
-900 onwards Bronze Age
-1400 beginning of modern man (homo sapiens sapiens)
-1500 beginning of Neanderthal man
between -2000 and -1600 beginning of Erectus.
Since Erectus only left the two poor strata like at Swanscombe or El-Castillo/Spain, he should actually not have lasted longer than Neanderthal-may be one average life expectancy. I will now not go into the mechanism of mutation. All I want to remind you of is the undisputed sequence of interstratification and monostratification in the master stratigraphies. This allows for one solution only: Parents of the former developmental stage of man lived together with their own offspring in the same cave stratum until they died out. They were not massacred as textbooks have it:
monostrat.: only modern man's tools
interstrat.: Neanderthal man's and modern man's tools side by side
monostrat.: only Neanderthal man's tools
interstrat.: Neanderthal man's and Erectus' tools side by side
monotstrat.: only Erectus tools (deepest stratum for intelligent man)
The year figures certainly sound bewildering. Yet, so far nobody came up with any stratigraphy justifiably demanding more time than I tentatively assigned to the age of intelligent man. I always remind my critiques that one millennium is an enormous time span--more than from William the Conqueror to today's Anglo-World. To add a millenium to human history should always go together with sufficient material remains to show for it. I will not even mention the easiness with which scholars add a million years to the history of man until they made Lucy 4 million years old. The time-span-madness is the last residue of Darwinism.