One problem with asserting microcephaly is that there are already 185 distinct genes (see the SAITO screenshot at the bottom) implicated in different kinds of microcephaly. Could that number rise dramatically? Sure – there are projects underway looking at eight different chromosomes to understand both deletions and ring chromosomes. And those would be just genes from living homo sapiens. So a key question is: Is someone claiming ALL the Homo floresiensis were micro-cephalic or just the one (LB1, also known as “Flo”)
Another conjecture to explain Homo floresiensis was advanced in
Evolved developmental homeostasis disturbed in LB1 from Flores, Indonesia,
denotes Down syndrome and not diagnostic traits of the invalid species Homo
floresiensis Henneberga, Maciej; Eckhardt, Robert B.; Chavanavesb, Sakdapong;
Hsü, Kenneth J.
Proc Natl Acad Sci USA. 2014;111(33):11967–72. pmid:25092311
Like microcephaly, the simplicity of the name Down Syndrome belies a great deal of complexity. There are presently at least four types of Down Syndrome: complete chromosome 21 trisomy where virtually all cells in the body have three copies of chromosome 21 instead of the usual two; incomplete chromosome 21 trisomy where virtually all cells in the body have two and a fraction copies of chromosome 21; incomplete chromosome 21 trisomy with translocation where virtually all cells in the body have two and a fraction copies of chromosome 21 AND the fraction is attached to some other chromosome; and mosaic chromosome 21 trisomy where some cells in the body have two and a fraction copies of chromosome 21. If any reader knows of a paper announcing a mosaic situation with a complete third copy we would appreciate a link. Likewise, if any reader knows of a paper that discusses what other chromosomes get supplemented with pieces of chromosome 21 during translocation we would appreciate a link.
In Baab KL, Brown P, Falk D, Richtsmeier JT, Hildebolt CF, Smith K, et al. (2016)
A Critical Evaluation of the Down Syndrome Diagnosis for LB1, Type Specimen of Homo
floresiensis. PLoS ONE 11(6): e0155731. https://doi.org/10.1371/journal.pone.0155731 the authors disagree with the assertion of Down Syndrome. We are inclined to agree with their points.
However, if the claim is many or most of Flo, her family and her friends had microcephaly or Down Syndrome, we’d be curious how such a population apparently survived 150,000 years making stone tools; perhaps managing fire; maybe even having language; not being wiped out by tsunamis, earthquakes and massive volcanic eruptions; hunting admittedly smallish elephants; and avoiding giants storks and Komodo dragons.