Is it possible for the phenotypically white people to produce a phenotypically black child?
i meant two instead of the
It’s quite easy, and it happens all the time. Because ‘black’ is an arbitrary concept, the genetic difference between a phenotypically black person and a phenotypically white person is only one gene. At some point you arbitrarily decide that a skin hue lighter than X is white. If two people who barely slip into the white category have a child there is a reasonable chance that the child will be marginally darker than either of them and will have to be assigned as black.
As you can see, the problem comes from trying to define phenotypically white. Skin colour genetics is poorly understood in humans, but as far as we know two extremely fair-skinned, blonde haired people can not produce a baby with exceedingly dark skin and black hair. The ability to produce melanin is apparently dominant, although it isn’t simple dominance. However most phenotypically white people aren’t extremely fair, and most phenotypically black people aren’t exceedingly dark. There is no known reason why two moderately light skinned, dark haired people can’t produce a moderately dark skinned and black haired child. It would be unusual, but there is no known reason why it couldn’t happen.
As Blake says, random slight variation is normal. However, if we’re talking very white parents producing a very black child: no. See this article, How do we inherit our skin colour?, which examines in some detail the long-running myth of the ‘throwback’ (“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”). When you get cases that appear to support this - e.g. Sandra Laing - my first thought is “DNA test”.
While the ‘Multiracial Activist’ site given by raygirvan is very broadly correct, it uses far too many absolutes to consider it to be accurate. It is also hopelessly out of date technically. You will note if you peruse the references that all the genetics material is 20 years or more old, and I don’t think the author understood that. The genetics of human skin colour is still not well understood, and a lot of it is extrapolated from animals and is known to be flawed for this reason. However we do know that there are no special black ‘dark skin genes’, and that whole page relies on the existence of such genes.
For example it states that if a ‘white’ and a ‘mulatto’ have children “the child will always be lighter in color than the other mulatto parent whether dark or light-complexioned” beacsue it will oinherit “the light skin color genes from the white parent”. However it goes on to say that “When two mulattoes of any degree mate” they “can produce a child darker than either parent” because “the child can get all or most of the dark skin color genes from both parents”. This is discredited nonsense. Any two people can produce a child that is darker than either parent. There are no specifically black/mulatto ‘dark skin colour genes’ and there are no specific “light skin color genes” omn;y available “from the white parent”. They just don’t exist. By chromosomal allocation any child can inherit more genes for dark colouration than possessed by either parent. While this may be more likely in people of recent mixed racial ancestry, it is a common enough occurrence for ‘pure’ Caucasians to be darker than either parent, as I am sure we’ve all experienced even within our circle of friends.
If nothing else the assertions of that site can be countered by logic. Egyptians and southern Mediterraneans are effectively all ‘mulatto’. If one were to select the darkest person in Egypt, no matter who she has children with the children could not be as dark as her because they must be less dark than the darkest (mulatto) parent. But then they in turn will produce children less dark than they are and so forth. By this reasoning everyone in Egypt and the Mediterranean must be growing progressively lighter each generation. It can only be by a fantastic rate of mutations leading to darkening that we still see so many olive skinned Egyptians and Italians. It’s obvious eugenecist nonsense. Egyptans and Italians are not getting lighter. Some Egyptian children are darker than both their parents and some lighter, just as is the case amongst ‘pure’ Caucasians and ‘pure’ Negroes couples.
So to rephrase: two fair-skinned, blonde haired blue eyed parents probably can’t have a black child. Two brown haired, brown eyed olive skinned people probably could but it would be exceedingly rare. A ‘mulatto’/Caucasian couple can indeed have a child that is darker than either parent despite what that website claims. In theory that child could be ‘black’. Highly unlikely, but genetically possible.
Is skin color determined by just one gene?
Also, the OP doesn’t define what is meant by “black” and “white”. Most people define both phenotypes to consist of more than just skin tone (ie, hair color and texture, as well as facial features).
Nope, I said that “the genetic difference between a phenotypically black person and a phenotypically white person is only one gene”, not that there is only one gene determining whether a person has black skin. There are at least 4 different genes at work on skin colour alone and it’s almost certainly 6 or more, but these have yet to be isolated. But that doesn’t make any difference to the example given.
Take a hypothetical man and woman. They are both barely able to scrape into the category ‘white’. Aside from the sex chromosomes both are genetically identical except at one location: the woman has a functional pigment gene on chromosome 12 and the male has a functional pigment gene on chromosome 16. There is a 25% chance that a male child from such a union will be genetically identical to the father in all respects except that he will also inherit the functional gene from the mother on 12. He will still have the functional genes from the father on 16. The child will be genetically different to the father solely in having one additional functional pigment gene, but as a result will be darker than his father. Since the parents barely scraped into being white the child will necessarily have to be classified as black. That is what I meant when I said that the difference between black and white is only one gene. It can’t be otherwise.
It doesn’t matter how you define or what characteristics you use. So long as skin colour is a factor the above statement remains true. In the example given above simply assume that both parents barely scrape into the category of white in all respects including hair colour and texture and facial features as well as skin colour. It doesn’t change anything at all. The child will still have borderline facial features and hair colour and texture but will have black skin. The child must be classified as black.
If you need clarification, think of how you are classifying. It has become an average score. If a person scores an average of >50 on blackness then he is black, and if less than that he is white. The parents scorecard look like this:
Skin colour: 50
Facial features: 50
Hair colour: 50
Hair texture: 50
Average of 50. They are white.
The child’s scorecard on the other hand looks like this:
Skin colour: 51
Facial features: 50
Hair colour: 50
Hair texture: 50
Average 50.25. The child is black.
It doesn’t matter how many characteristics you use or what your cut-off value is for each race. Because racial classification is totally arbitrary the difference between one race and another will always be only one gene. Because the difference between one race and another is only one gene there will always be a reasonable chance for children of white parents to be black and vice versa.
Blake:
OK, I understand what you’re getting at. I read your original statement: “the genetic difference between a phenotypically black person and a phenotypically white person is only one gene” as “the genetic difference between a phenotypically black person and a phenotypically white person is always only one gene” when you meant “the genetic difference between a phenotypically black person and a phenotypically white person can be only one gene.”
So, I guess it depends on what the meaning of “is” is, after all.
Skin color is a minor factor in racial differences. Its quite easy to differentiate between a caucasian albino and a negro albino, despite their similarities in skin tone.
Absolute nonsense. I just finished explaining why this could not be the case in some detail.
Because there is no clear boundary whatsoever between races that statement cannot possibly be true. At some point there must be an individual that is defined as negro solely because of skin colour while an otherwise identical person is considered white. This is true of most Ethiopians for example. If such a person where albino they would not be any way at all of telling they were negro.
For example, look at the Ethiopian men in the last photo on this page. (http://www.icsep.org.il/about/quotes.shtml). In particular note the man on the far right, who is clearly a Negro. Absent skin colour how excatly could you distinguish him from this man ( http://www.webtravelguide.de/Bilder/Libyen/3.htm ) who is clearly not a negro? You can not give any objective reason for classifyong on as black and one as white absent skin colour.