It was once thought that humanity was divided into separate species, roughly along the lines of the traditional ideas of separate races. We now know this to be false. Just as all dogs, from rottweilers to chihuahuas, belong to just one species, so too is there only a single species of humans.
Kelly, Yvonne; Sacker, Amanda; Schoon, Ingrid; Nazroo, James (2006) Ethnic differences in achievement of developmental milestones by 9 months of age: the Millennium Cohort Study, Developmental Medicine & Child Neurology 2006, 48: 825–830.
4:54
3:30
4:00
3:53
5:04
4:36
3:51
5:07
5:11
4:26
9:03
5:53
5:47
2:24
