Head colours?

[jusdeb]

From a lesser nerdy type person I accept your apologies but I gotta tell you it has been great reading and I may have even learnt a thing or two .

Good subject , good answers and lots to ponder .

[Nrg800]

Umm! Thanks so much for those answers! I think I can follow it all! I can't wait untill we start doing interesting Biology in school (Right now we've learnt, well... About like, the various body systems). Do you know any good textbooks I can get about this? Chemistry has nothing on Biology!

Thanks!
Nathan!
P.S. You could also cite Jurassic Park for the amphibian thing!

[Nrg800]

Well, while we're asking difficult (off topic) questions... Why is it that interbreeding between human 'races' has no adverse affects. I know we are all Homo sapien sapiens, but, like. We split 50,000 years (2,500 generations) ago, and yet. Well, honestly, not only are inter-racial people completely free of haldane's rule, they are also (in my opinion) quite attractive... As good as Biology is, it has quite a few difficult questions!

Thanks
~Nathan

[Niki_K]

Well, while we're asking difficult (off topic) questions... Why is it that interbreeding between human 'races' has no adverse affects. I know we are all Homo sapien sapiens, but, like. We split 50,000 years (2,500 generations) ago, and yet. Well, honestly, not only are inter-racial people completely free of haldane's rule, they are also (in my opinion) quite attractive... As good as Biology is, it has quite a few difficult questions!

Thanks
~Nathan

Basically, because we haven't diverged enough. For a partial divergence (i.e. to create a subspecies that may interbreed but not necessarily produce viable offspring), you need a minimum of 200,000 generations. For complete isolation, you're looking at upwards of 350,000 generations. This assumes completely isolated populations, which is extremely unlikely to occur presently in humans, as there have always been cases of people moving from society to society, thus interbreeding and passing on their genes.

[finchbreeder]

From someone who is strictly a gene carrier for highly genetically/scientifically competent types. Mum is brilliant with bird genetics and daughter just missed a High Distinction in Undergrad Genetics by 2%. I can only say is seems to me that one of the reasons some species mutate more than others would be the faster breeding cycle. e.g. if you do 1 generation every 50 years you will not have anywhere near the opportunity to mutate as if you do 1 generation every 5 months. Locical as Spok would say.
LML

[mattymeischke]

Well, while we're asking difficult (off topic) questions... Why is it that interbreeding between human 'races' has no adverse affects. I know we are all Homo sapien sapiens, but, like. We split 50,000 years (2,500 generations) ago, and yet.

Interbreeding between human races is analagous to putting pied zebs to fawn zebs: we wouldn't expect any adverse effect from that pairing. Now interbreeding between human species , that's a little more interesting. We have good evidence of neanderthal DNA in the modern human genome. It is still a subject of passionate debate, but it seems that H. sapiens and H. neanderthalis are distinct species and that they interbred fairly frequently, though the circumstances in which they did so remain a matter of rank speculation. Haldane's rule may have applied to this hybrid pairing.
It is difficult to apply science to this speculation.

Haldanes rule would also apply to other hybrid pairings, like a humpanzee (chiman?).

The reason why Haldane's rule applying in Gouldians of different head colours is so interesting is because it implies that the different head-colour morphs of Gouldians are well on the way to becoming different species, as opposed to variations of the same species.

It strikes me that it is probably beneficial to interbreed between 'races'; many subgroups of humans have rare genetic disease, transmitted as autosomal recessive genes. An example is Tay-Sachs disease, which most commonly occurs when Ashkenazi jews get two copies of a particular abnormal gene. However, if they carry only one copy they do not get the disease, but seem to have a higher intelligence that those who carry no copies of the abnormal gene. Another example is a family of enzyme disorders which make red blood cells fragile. These disorders might make people susceptible to death when they get infections, or in one of the syndromes (known as favism) they may have a fatal reaction to broad beans. However, they confer protection against malaria, as the parasite cannot reproduce in the fragile red blood cells, so the malarial disease cannot progress. By breeding with genetically distinct individuals, one minimises the risk of these rare problems, while maximising the possibility of the beneficial heterozygote condition for progeny. Australian aboriginal marriage customs and clan rules have been posited as one example of social mechanisms to ensure 'out breeding' and avoid 'in breeding'.

Well, honestly, not only are inter-racial people completely free of haldane's rule, they are also (in my opinion) quite attractive...

Well, Nathan, that's outside my area of expertise. However, I can say that breeding out improves vigour, and that breeding in tends to accumulate deleterious mutations.

[MadHatter]

To come back to the subject of gouldians and the apparent conflict between the experimental results of Ms. Pryke and the anecdotal experience of breeders, it seems to me that there may be a simple explanation. It stands to reason that Ms. Pryke's experimental colony was most likely sourced from wild birds and is probably only a comparitively few generations removed from the wild founders, whereas our domestic stock must be many more generations removed from the original wild-caught founders, and we have been indiscriminately breeding the different head colours to one-another for a great many generations. (N.B. the word 'indiscriminately' is not intended perjoratively in this context)
It seems entirely plausible to me that we may have inadvertently bred out the incompatible alleles from our domestic strains.
If that is the case, then we may prove to have unwittingly altered the domestic bird far more than we had ever realised.

[Niki_K]

To come back to the subject of gouldians and the apparent conflict between the experimental results of Ms. Pryke and the anecdotal experience of breeders, it seems to me that there may be a simple explanation. It stands to reason that Ms. Pryke's experimental colony was most likely sourced from wild birds and is probably only a comparitively few generations removed from the wild founders, whereas our domestic stock must be many more generations removed from the original wild-caught founders, and we have been indiscriminately breeding the different head colours to one-another for a great many generations. (N.B. the word 'indiscriminately' is not intended perjoratively in this context)
It seems entirely plausible to me that we may have inadvertently bred out the incompatible alleles from our domestic strains.
If that is the case, then we may prove to have unwittingly altered the domestic bird far more than we had ever realised.

Excellent point. As far as I am aware, Sarah Pryke's colony are wild-caught descendants (though I'll try and confirm this). With the short generations that finches exhibit, it is possible that interbreeding head morphs in aviaries is causing a 'pre-divergence' if you will, where the effects of interbreeding are minimal.
Apart from colours, I do see differences in behaviour between my wild-type and domesticated zebs, primarily that the domestics are more willing to breed in the breeding cages and appear calmer around people.

[Tiaris]

I very much doubt they were wild caught birds.

[Niki_K]

I very much doubt they were wild caught birds.

They're definitely not wild-caught birds. They're wild-caught descendants. However, I do believe she also has a domesticated colony.