Well, we can be reasonably certain they don't because we have a better explanation in place. It doesn't seem so with the language thing. Is the idea that our ancestors migrating out of Africa had some sort of rudimentary language- including concepts for the top few of the "basic colours"- so far fetched as to be in the same plausibility class as bread-fairies?
Depending upon which ancestors we are believing wandered out of Africa, possibly. The usual "out of Africa" hypotheses are not about humans, but about hominid ancestors that do not appear to have either the cranial capacity
or vocal capacity for human-like speech. My understanding is that the jury is still out on whether or not Neanderthals had the capcity for human-like speech, and those are considered to be a subspecies of
Homo sapiens.
At some level, of course, you are right. At some point in time the entire population of (the appropriate subgroup of)
H. sapiens was presumably small and geographically isolated in one point, and at that point,
if they had a language of their own, it was presumably shared among the entire subgroup. But there's literally no evidence that we can point to that suggests that language was this early an innovation; many anthropologists believe that language was a later development that happened in many different areas independently.
But their efforts aside, given the evidence from biology and such that we did all come from a common ancestry, isn't a common basis for language the most parsiminous explanation for the colour thing?
No, it isn't. See below.
Why would we? We don't see different patterns of numbers of legs, do we? Let's say that we have Bob, Doug, and Milo, and they all speak Proto. Proto has a word for Black (Ugh), a word for White (Guh), and a word for Red (Hug). Bob's ancestors migrate to Asia, Doug's to Europe, and Milo's stay in Africa. Along the way, Bob's decendents have started pronouncing the word Ugh so it sounds like "Uck", while Doug's say it like "Mug" and Milo's "Og." They are similar changes that happen to "Guh" and "Hug." This does not change the order in which the colours were named.
The reason we don't see different patterns of numbers of legs is because we don't see different numbers of legs (by and large). When we do see genetic variation from the "typical" (e.g., polydactyly), it usually comes in genetic groups. What we rarely see is multiple independent reinventions of genetic variation.
So let's look in more detail about our hypothetical distribution of languages. The problem with your common-ancestry hypothesis is that it doesn't account for the uniform hierarchy of color names. Specifically, some inquiring mind among Milo's descendents discovered a new color, almost certainly green or yellow. Similarly, some inquiring mind among Doug's decendent's also discovered a new color --
also green or yellow.
Why should Milo's children independently discover the same color as Doug's? Why didn't Doug's children discover "grey" or "blue" or "brown" instead? And why should Bob's children
also discover green and not grey or brown?
Furthermore, we would expect to see that the children of Milo's children would inherit their language from one of Milo's children -- which means that the descendents of the child who invented green would have and use a word for green, while the children of children who didn't know about green wouldn't.
In genetics, where descent-with-modification is about the only explanation for change that we have, scientists have no problem patching all the various groups together into substructures and family relationships. Similarly, in recent historical linguistics, we again have no problem putting the substructures together. Dutch, for example, is closer to English than it is to German; German is closer to English than to Danish. We're currently working out a theory of how various Indo-European groups relate -- e.g. whether Danish is closer to French, Greek, or Russian. If the color hierarchy really had been related to descent-with-modification, we should see inheritance patterns in the colors at extremely gross levels. We don't.
Wikipedia: "(in Nicaragua) Deaf people were largely isolated from each other, and used simple home sign systems and gesture ('mimicas') to communicate with their families and friends."
That doesn't sound ex nihilo to me.
There's a difference -- practically a watershed -- between "sign systems and gesture" and "language." The "sign systems" used by NIcaraguan deafs weren't language, and the deaf children were barely above the cognitive level of "wolf children" for exactly that reason.
In particular, the idea of "concepts that the parents pass on to their children" presumes a level of communicative -- and cognitive -- ability that was simply not present. One of the scariest films that I've seen involved pictures from some of these children (and now adults) in appropriate support contexts.
You could tell just by watching the films who the ones who got early intervention were. Even without any knowledge of what they were "saying," they were the ones who were obviously signing in language, not in gesture systems. They had fluency, they had syntax, they had body language going. The ones who had not received early intervention were stumbling through from sign to sign to sign in a kind of "you tarzan me jane" pidgin
at best.
Reading the transcripts just made it that more obvious.
The point, of course, is that the parents didn't "teach" their children much if anything. The language more or less spontaneously appeared
when sufficiently young children were put
together in a communicative context.
