Kevin's Watch

berk peter wrote:but I equally contend that a random mixing of the currently found genetic allele's that go into making up all the different types of physical atribute visible in the various 'races' today, would likely produce a human appearance somewhat different to that which we commonly see;

I'm not sure of that...maybe. Probably "uncommon" appearance...but not unheard of/unprecedented. There are very likely some walking around right now. Some likely places to look: India, and close by. Vietnam and Japan and Korea and the Philippines...especially the Philippines I'd say. [just thinking on U.S. military alone, there have to be some...cuz some percentage of white personnel are partly black, and some percent of black are partly white...and there have been 10's of thousands of the multi-mixed children born...some places [especially Philippines] there are multiple generations of such.

I was about to reply Mongnihilo, that Neanderthals *were* the same species as modern man - but decided to check my facts first. It transpires that what I remember as Homo sapiens neanderthalis [from many moons ago] has subsequently been reclassified as simply Homo neanderthalis, and hence has moved from within to without the species of which we are [currently] the only surviving sub-species [always asuming we are indeed still classified as Homo sapiens sapiens].

An interesting point re interspecific breeding is that it is not [as I understand] a 'genetic' correspondence or otherwise that allows or precludes it, but rather a 'chromosomal' one. The pairing of chromosomes and subsequent sepparation in the reduction division {meiosis} requires a bipolar spindle formation that I believe will not occur [possibly wrong here] if the chromosomal correspondence between the two reproductive cells is not close enough. {The situation where no offspring of a coupling is produced}. If the correspondance is close enogh to allow spindle formation - but not close enough for proper meiotic division to occur in the daughter cell produced, the zygote thus formed will develop into a cross-specific individual - but this individual will be a sterile 'mule' [a name not specific to the horse/donkey cross but applicable to any interspecific infertile individual. It is the inability of chromosomes to pair in their appropriate [male/female] pairings when this 'mule' in turn, attempts to produce viable reproductive cells by meiosis, that renders it infertile. This - I believe - was the basis of the [one time] critereon, that if two individuals could produce a fertile offspring, then they were of the same species. [All this is dredged up from long long ago so forgive me if the details are not absolutely correct!] Hence my suprise to see that this rule now no longer seems to be applicable [still nothing lasts for ever ]

[nb I have heard of examples where interspecific crosses have produced cells viable for further cell division, but was this not only when the cells were artificially treated to produce a doubling of the chromosomal number, which in itself causes problems due to the exagerated size of the nucleus required to contain the mass of chromasomal matereal thereby produced - a purely 'mechanical' limitation pertaining to surface areas to volume ratio's etc.]

Inter species hybridization is a known phenomenon, and it can produce viable offspring. Google sind seinem Freund.

Will do. No doubt you are correct, but whether it contributed to a significant degree in the formation of 'us', I would [as yet] maintain a healthy degree of scepticism.

The problem here has got to be one of the imposition of arbitrary boundries on that where no natural boundries exist. One could go so far as to say that the concept of 'species' is effectively redundent at the level of closeness we are talking about. The only criteria of evolutionary signifficance is whether two individuals are closely enough [chromosomally] related, to produce fertile offspring - or not.

Not necessarily. Hybridization may greatly affect fitness in a number of ways, and in the case of human-Neanderthal hybrids, in some ways their fitness appears to have increased and in other ways decreased. But mother nature found a way to get the necessary traitsinto the genome.

Mongnihilo wrote:Not necessarily. Hybridization may greatly affect fitness in a number of ways, and in the case of human-Neanderthal hybrids, in some ways their fitness appears to have increased and in other ways decreased. But mother nature found a way to get the necessary traitsinto the genome.

The concept of 'hybrid vigour' has been around for many years [the Olympic decathelete Daley Thompson was even touted as an example of it {I believe} in my day], but always [in my day] within the boundries of one species. [Again I hark back to the definition thing here - a 'species' being only what we decide it to be, and overlayed [as a classificationary tool] on top of a 'continuum' of living organisms].

Obviously we are discussing human abstractions assembled with less than fully rational heurisms, but I think those abstractions are still significant and meaningful, and ought to be treated with rigor. And when we are discussing "species," the categorical heurism goes beyond fertile offspring:

www.gate.net/~rwms/hum_ape_chrom.html

We have all heard that the horse and the donkey produce an infertile mule in crossing because of a different number of chromosomes in the two species. Well, apparently there is more to the story than we are usually told, because variations in chromosome number are known to occur in many different animal species, and although they sometimes seem to lead to reduced fertility, this is often not the case. Refs 5, 6, and 7 document both the existence of such chromosomal number differences and the fact that differences do not always result in reduced fertility. I can provide many more similar references if required. The last remaining species of wild horse, Przewalski's (sha-val-skis) Wild Horse has 66 chromosomes while the domesticated horse has 64 chromosomes. Despite this difference in chromosome number, Przewalski's Wild Horse and the domesticated horse can be crossed and do produce fertile offspring (see reference 9).

Vraith wrote:Yea, I don't want to get too far off topic, but some things aren't as clear/set/understood as it sometimes seems.
Like the folk that are XXX, XYY, XXY [I think there are even folk with 4??]
Clearly "All human"....just a bit EXTRA human...

But these V. are clear cases that result from failure of chromosomal sepparation in the parental generation prior to zygote formation [and subsequent development of the individual], not as a result of interspecies cross. [Nor am I at all sure that these individuals are by any means all 'fertile'.]

Having said that do take on board Mong's position - clearly much has occured at the level of 'cell biology' since my [badly absorbed] lectures on the subject. It does seem to me however that if you pull away the 'fixed ground' beneath your definitions in science, you had best be able to replace it with equally clearly understood 'boundries' [not withstanding what I have said in previous posts] or the risk in breakdown of effective 'communication' and [a concurrent increase in 'fuzziness'] is greatly increased.

Species is a fuzzy concept, like any other synthetic a posteriori category. But that doesn't make it meaningless. Perhaps there will prove to be better models to encompass the process of speciation, which is poorly understood at this point.

Mongnihilo wrote:Species is a fuzzy concept, like any other synthetic a posteriori category. But that doesn't make it meaningless. Perhaps there will prove to be better models to encompass the process of speciation, which is poorly understood at this point.

Agreed. In many...almost all...ways "race" is extremely fuzzy for humans...yet some things matter. I mean being "black" has pretty much zero real relevance as far as competence, intelligence, etc. etc. etc. [a very long list of etc.'s.]
BUT: there is no doubt that being black, especially being very purely black, means you are far more likely to have sickle-cell.
The differences, which spiteful/ignorant/hateful people latch on to, are very particular/specific/local...but those folk generalize them.
The differences they generalize them INTO are false...because they are, biologically, the opposite of sickle-cell. Complex, interactive, widely distributed.
As it interacts with environment, I suspect some fuzziness there, as well...too much difference, no breeding [or at least unsustainable fertility/survival rates] is possible. BUT, the other end: too MUCH similarity compounds the extremes...and limits adaptability [which are not the same thing even though the long term result is the same].

Mongnihilo wrote:Species is a fuzzy concept, like any other synthetic a posteriori category. But that doesn't make it meaningless.

Absolutely not, but equally one must never forget that is a 'classificationary tool' no more, no less, and that as such 'nature' will never respect it's boundries just to suit us.

Peter, I couldn't agree more. Species seems to indicate more than anything a quantitative genetic distance that at some point becomes qualitative. I think forms such as Neanderthal are standing on the shoulder of such a transition vis-à-vis modern humans, and yet it's also clear from the genetic evidence that a significant amount of genetic distance existed at the time, enough to cause major impacts to the fertility of offspring. It is hard to regards the breeding events as fusion rather than hybridization. There are also many other morphological differences including cranial, which indicate a significantly distinct series of adaptations and, most likely, culture. So there is definitely an alien quality to these beings. We must deduce that they thought and acted in distinct ways from our ancestors.

berk peter wrote:

Mongnihilo wrote:Species is a fuzzy concept, like any other synthetic a posteriori category. But that doesn't make it meaningless.

Absolutely not, but equally one must never forget that is a 'classificationary tool' no more, no less, and that as such 'nature' will never respect it's boundries just to suit us.

Heh, I agree basically and with some overlap with things Mong. already said.

As long as what we mean is that 'classification' is NOT arbitrary/infinitely variable, nor is it absolute IN GENERAL [though it may be in PARTICULAR].

For instance in the extreme [I MAY be wrong/out of date with this, discoveries may have occurred that make one or the other part false...but not the conclusion]
There ARE plants that are 'male' or 'female'...just like there are wolves that are male or female. But in no case could the male or female of a plant screw a male or female wolf [or vice versa] and produce anything of any species.
classification is binary [in or out of a class] but also contextual and relative [randomness, viewpoint, and "nearness" matter].