I recall this term being used in the 60’s by an older relative to describe a neighbor child who was mildly mentally retarded and had vaguely “cavemanish” (protruding brow, deep set eyes etc) look about him. The relative called him a “throwback”.
While I doubt this was the case for this poor child I am curious if genetic “throwbacks” actually exist in any form in nature where an earlier, slightly less evolved (not retarded) form of a animal/mammal might be occasionally produced from two otherwise normal parents, or is what are considered throwbacks almost always simply various forms of retardation or.
Not sure what you mean by “slightly less evolved”. There have been cases where “primitive” characteristics in a population of domesticated animals have been selected for to “recreate” the ancestral wild “type”. In a sense, you can call the animal that results a “throwback”. For a description of this process, see:
I would go as far as to say that these efforts to recreate ancient forms of species will be more successful than reproducing creatures from fossilised DNA, and if we ever recreate the mammoth it will mostly be by this route.
So, are humans ever born with traits one could accurately classify as “more primitive” than our current standard homo sapiens genotypical template?
Furthermore if you could get a male and female with these more primitive characteristics, could you (theoretically) breed back to an earlier form of humanity… or am I confusing myself about what the term “breeding back” means this context with respect to evolution.
As far as the retarded neighbor is concerned, whatever genetic anomalies caused the low IQ also caused phenotypic changes that you are interpreting as neaderthal in appearance. He did not suddenly revert to the distant past. OTOH, traits not seen for many generations, conceivably even thousands of years can suddenly appear. These atavistic traits are caused by long dominated recessive genes suddenly finding another of its kind and expressing itself. Easy to identify in fruit flies, much harder in humans.
I’m a throwback. Any anthropologist will confirm that the trend lately has been for humans to have fewer teeth. I have an extra pair of molars in line next to my wisdom teeth. No brow ridge, though.
Truthfully speaking, although the selective breeding programme for, say, theQuagga might produce an animal which resembles the original physically, it is unlikely to have the innate behaviours and instincts of the original subspecies. This difference would be even more marked ifa mammoth were successfully recreated…you could use the DNA scraps discovered by palaeontology as a guide, but as there is only about 3x10^-6 of Mammoth DNA currently available this might be difficult.
The same would happen if you tried to recreate* Homo erectus,* for instance (neadertalensis might be even more difficult, because this species existed on a seperate branch, apprently with little or no interbreeding), and you might end up with an entity that resmbles the target, but behaves differently.
Genetic forms of mental disability, such as ‘fragile x’, by the way, have no atavistic traits at all, as far as I know… if the skull is smaller and the brow ridges protude in certain genetic disorders, this is unrelated to the evolution of H.sapiens.
Relevant news item: the case of Sandra Laing. See The black woman - with white parents (pics here at SA Sunday Times). I’m seriously, seriously dubious about this particular ‘throwback’ claim - yet no-one seems to be questioning it and suggesting the obvious alternative explanation.
I’d be happier with a modern DNA test. If it was a simple ABO test (quite possible 30 years ago) there’s a reasonable chance of a false positive. Besides, this appears to be an old and questionable idea in that region: see How Do We Inherit Our Skin Color? on the subject of atavism (‘In 1972, for example, sociologist Ian Robertson and commentator Phillip Whitten reported that some whites in South Africa still utilize “the genetic throwback” to account for a mulatto birth to white parents’).
In 1967, the only thing that a blood test could prove would be if the child’s blood type could be produced from the blood types of the parents. If the child is type O, then parents could be type O, type A, or type B, but not type AB. Well, it just so happens that race does not determine blood type.
In other words, the blood test cannot prove paternity nor maternity, it can only exclude–and even then not necessarily.
