I want to see the proof that H. sapiens could in fact interbreed with erectus, neandertalensis, and heidelburgensis. Or for that matter, that erectus and neandertalensis could inertreed, or that erectus and heidelgurgensis could interbreed, or any other combination (seeing as how the MRH requires them all being able to interbreed, from what I understand).
While so far the evidence for hybridization is weak and mtDNA evidence seems to suggest that there was no gene flow between H. neanderthalensis and H. sapiens, it doesn't rule it out entirely. A study done by Clifford Jolly on the Papionina subtribe of monkeys suggests that hybridization can occur between hominine genera that have diverged as long as 4 mya. It is possible that advantageous genes survived as the hybrid zone shifted. (Jolly, CJ. 2001. A Proper Study for Mankind: Analogies from the Papionin Monkeys and Their Implications for Human Evolution. Yearbook of Physical Anthropology. 44: 177-204).
Here is a paper that suggests that there was some hybridization between the populations: Hardy, J. et al. 2005. Evidence suggesting that Homo neanderthalensis contributed the H2 MAPT haplotype to Homo sapiens. Biochemical Society Transactions. 33: 582-585
quote:
ABSTRACT: The tau (MAPT) locus exists as two distinct clades, H1 and H2. The H1 clade has a normal linkage disequilibrium structure and is the only haplotype found in all populations except those derived from Caucasians. The H2 haplotype is the minor haplotype in Caucasian populations and is not found in other populations. It shows no recombination over a region of 2 Mb with the more common H1 haplotype. The distribution of the haplotype and analysis of the slippage of dinucleotide repeat markers within the haplotype suggest that it entered Homo sapiens populations between approx. 10000 and 30000 years ago. However, sequence comparison of the H2 haplotype with the H1 haplotype and with the chimp sequence suggests that the common founder of the H1 and H2 haplotypes was far earlier than this. We suggest that the H2 haplotype is derived from Homo neanderthalensis and entered H. sapiens populations during the coexistence of these species in Europe from approx. 45000 to 18000 years ago and that the H2 haplotype has been under selection pressure since that time, possibly because of the role of this H1 haplotype in neurodegenerative disease.
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