The following is the abstract from J.P. Rushton’s original 1989 paper that launched him to international controversy:
Genetic distance estimates calculated from DNA sequencing indicate that in years since emergence from the ancestral hominid line, Mongoloids = 41,000, Caucasoids = 110,000, and Negroids = 200,000. Data also show that this succession is matched by numerous other differences such that Mongoloids > Caucasoids > Negroids in brain size and intelligence (cranial capacity = 1448, 1408, 1334 cm3; brain weight = 1351, 1336, 1286 gm.; millions of excess neurons = 8900, 8650, 8550; IQ = 107, 100, 85); maturational delay (age to walk alone, age of first intercourse, age of death); sexual restraint (ovulation rate, intercourse frequencies, sexually transmitted diseases including AIDS); quiescent temperament (aggressiveness, anxiety, sociability); and social organization (law abidingness, marital stability, mental health). This pattern is ordered by a theory of r/K reproductive strategies in which Mongoloids are posited to be more K-selected than Caucasoids and especially more than Negroids. (K-selected reproductive strategies emphasize parental care and are to be contrasted with r-selected strategies which emphasize fecundity, the bioenergetic trade-off between which is postulated to underlie cross-species differences in brain size, speed of maturation, reproductive effort, and longevity.) It is suggested that this pattern came about because the ice ages exerted greater selection pressures on the later emerging populations to produce larger brains, longer lives, and more K-like behavior. One theoretical possibility is that evolution is progressive and that some populations are more “advanced” than others. Predictions are made concerning economic projections and the spread of AIDS.
One especially interesting part of Rushton’s theory was the idea that later emerging populations are more advanced than early emerging populations, but Rushton never fully elaborated, beyond saying that Negroids emerged 200 kya, Caucasoids 110 kya and Mongoloids 41 kya.
Rushton’s source for these dates has always come from one 1988 paper from CB Stringer and P Andrews. Nowhere in the paper do they explicitly state that Negroids emerged 200 kya, so Rushton must have infered it from this paragraph:
If mtDNA changes are assumed to accumulate at a steady rate, genealogical trees constructed by minimizing genetic changes (through maximum parsimony analysis) distinguish two main branches. One leads exclusively to a number of African (or African origin) individuals, whereas the other leads to all other individuals of African or non-African origin. Dates for the branching points of the tree can be estimated from rates of mtDNA evolution in other organisms. This gives a date for the origin of the mtDNA of Homo sapiens at between 140,000 and 290,000 years ago, assuming constant rates of change at 2 to 4% per nucleotide site per million years…
Nowhere in the paper do they state that Caucasoids and Mongoloids emerged 110 kya and 41 kya respectively, but Rushton must have infered it from this paragraph:
Protein analyses, however, show a consistent split between “negroids” and the other groups, in accordance with most results from mtDNA and nuclear DNA. There mav be stronger selection on blood group types, and there is a less clear relationship between blood group phenotype and nucleotide sequence. Since the body of data from protein systems is also larger, the results from protein analyses are probably the most relevant here, and support the recent African origin model. These have been used to calibrate divergence times (again assuming selective neutrality and absence of gene flow) of about 110,000 years ago for the African-non-African split and about 41,000 years for the EuropeanAsian split (38).
In short, the paper seems to be saying the following:
So it seems that Rushton would have interpreted the above tree as showings Negroids emerged 200 kya, Caucasoids emerged 110 kya, and Mongoloids emerged 41 kya.
My reading of the tree would be Negroids emerged 110 kya and Caucasoids and Mongoloids both emerged 41 kya, if emerged is defined as branching off the main trunk of the human evolutionary tree.
Rushton once told me that he believed “Mongoloids branched off from Caucasoids in a superior form”, but his citation only claims a Mongoloids and Caucasoids split from each other, not that one split off the other.
Nonetheless Rushton was probably right. The last common ancestor of Mongoloids and Caucasoids probably looked and behaved more like a Caucasoid than a Mongoloid. If so, it seems reasonable to say Mongoloids branched off from Caucasoids.