Hmm - I’d found the Cecil column, and I’m not sure that’s what it’s saying. The random factors influencing fingerprint formation are neither fully enumerated nor well understood; there’s not really anything to suggest that even if we could control them (which I strongly doubt is possible), we’d be any more able to engineer identical twins with identical fingerprints than we would any given pair of foetuses. I certainly don’t think he’s saying that twins ever end up with identical prints:
We certainly agree that the patterns will be broadly similar, but given the very minor difference in biometric performance using samples from monozygotic twins, I still don’t agree that any unusual effort is required to distinguish between them.
Anyway, this is a bit of a hijack, and we’re not disagreeing that much.
No I agree that you could probably never control all of the variable in a person’s life. NOR would you even want to.
I was just saying that it’s not as simple as saying, “their fingerprints are different.” Sure they’re different, but not like mine and yours are different.
That is still a remarkable high propensity, isn’t it? By most accounts the total incidence of homosexuality in the general population is no higher than 10%, maybe no higher than 2%. Your studies would show that there’s definitely some genetic factor at work here.
I believe that each older brother in your family also somehow vastly increases the probability of you being homosexual compared to “chance” (ie. if there was no biological influence, be it genetic or ‘uterine’).
But one significant conclusion is that there are other factors beside genetic factors. In other words, that it is not a full explanation to state that a homosexual is the way he or she is because (s)he was born that way.
It may not be fashionable to say so, but if fighting ignorance is the aim, I can’t see any other conclusion.
I’m not sure what you’re saying is unfashionable. Current science says that genes are only one factor, and not the biggest one. That doesn’t take much steam of out the “born that way” thing, as I already explained.
I acknowledge it’s the personal opinion of one person, but Excalibre (and perhaps others) have spoken on these boards of the interplay of biological with environmental factors.
It would obviously be beneficial to gather more data of early childhood experience as recalled by individuals or recounted by observers in order to assess the effect of such environmental influences mroe accurately.
I don’t think a scientist would be looking for a common event but for a cluster of related events, so that tentative conclusions might be drawn. Whether people would be willing or indeed able to be interviewed is obviously a factor.
Not all biological factors are genetic. There appeas to be some important uterine chemical/hormonal factor which is not genetic but is still very definitely biological: If that were so, one would still most definitely be “born gay”.
(And even if there were some significant “nurture” factor, one still could not call this a “choice”. I certainly cannot remember choosing heterosexuality, or suppressing homosexual tendencies. Do you?)
Finally, roger, I hope that this discussion does not revert to an “Ah, but if we can’t prove that it’s impossible for homosexuality to be completely non-biological then I can conclude whatever I like!” position on your part. We both know where that approach got us last time.
The choice thing is passe (with an acute - can’t be bothered going to Word), SM.
What is of scientific interest is the relative contribution, and relative weighting, of biological and environmental factors.
Biological factors may be studied in various ways, as per the research studies referred to.
Environmental factors also allow of research through interviews and questionnaires. I will try to dig some up, and in the meantime would be glad of anyone who knows of such studies can post the results here.
Well, that post accurately expressed what I hoped would be the case: that if evidence showing a strong biological influence on the statistics were presented, you wouldn’t cling to the non-biological-causation position just because it was still possible even though it was strongly impugned by the evidence.
I’m not having a go at you here, roger: your critical thinking abilities seem to have developed greatly in your time on these boards. This is just a reminder that in any field of study we must consider the whole body of evidence and base our conclusions on the Bigger Picture. In this instance, the interplay between genes, uterine hormones and nurture is complex, precluding the citation of a single “killer fact” or definitive study. The Bigger Picture, I suggest, is clearly one of an incredibly important biological influence, to the extent that one is almost certainly “born gay”.
Despite having previously acknowledged the distinction, you are now ignoring the sort of biological factors that aren’t genetic, such as “prenatal wash”, if that’s what it’s called. Indeed, whether one is homosexual could be entirely epigenetic (i.e. unrelated to genes) and yet still be “how one is born”. Since it’s handily demonstrable that fingerprints are only partially genetically determined, your reasoning would lead us to conclude that my fingerprints are not as they are because I was born that way, but were determined after birth due to some other factor. Unless you think this is a sensible statement, your conclusion is entirely flawed.
Hi, I know this is part of a hijack and, as such, not really related to this thread, but I figure I’m in a pretty good position to tackle the whole fingerprints-amongst-twins issue, being a forensic investigator in training
The actual pattern of a fingerprint is created by the random arrangement of tissue build-up around sweat glands in the layer of the skin known as the dermal papillae (between the dermal layer and the epidermis). In these “friction skin” areas (palms, feet, ears even), the ridges are the only places where you have sweat pores. Dead Badger is right in saying that we don’t know exactly what factors influence the arrangement of these tissue build-ups, but it is clear that it is pretty random from person to person whilst still maintaining a pretty standard set of basic shapes (the arch, loop, whorls, composites).
Fingerprint identification involves several tiers of analysis. The first is the overall pattern, such as arch or loop. This is where most people differ - t-keela and Dead Badger probably have differing pattern sets on their hands. However, there are many many people who share the same basic pattern - and amongst my 25 classmates, there are two who have the same pattern set for each hand.
If two people have the same basic pattern on their finger, and it is not an arch, then we look at “ridge count”. This is the number of ridges that a straight line would cross over if it was drawn between the core - the centre of the fingerprint - and a delta point, which is where the fairly linear pattern at the edge of our fingers first separates to allow the pattern type to form. (This isn’t done for an arch because, by definition, arch patterns do not have deltas.)
If the two fingerprints have the same ridge count and overall pattern - which is not as rare as it sounds, especially not if you’re dealing with only one fingerprint compared to a database of them! - then minutiae are considered. This is where, I think, t-keela is getting the impression that twins’ fingerprints must be scrutinised more carefully than other fingerprints to find differences - perhaps a misinterpretation of the word minutiae. It is almost a given that a fingerprint examiner will have to go to the minutiae level to find a match. Any fingerprint database will have lots of fingerprints with the same pattern and ridge count.
Minutiae are little things that make two similar patterns different. Things like a very short ridge, or the place where one ridge splits into two - these are minutiae. Making any identification based upon fingerprints used to require 16 agreeing minutiae (in the UK - 12 in the US, 8 in Australia I believe), so it’s clear that this is a very standard procedure when looking at fingerprints, whether the source is two identical twins or two completely random people. This type of scrutiny is not unique to studies of identical twins’ fingerprints, but (as the study linked by Dead Badger shows) this is the level at which differences between twins’ fingerprints become apparent.
There are other, more microscopic details that are considered in fingerprint analysis as well - the precise shape of the edges of the ridge (ridgeology) and the distribution of the sweat pores along that ridge (poreology - forensic scientists like to make up words). It is not necessary to go to this level to find discrepancies between identical twins’ fingerprints - in fact, the only time it’s really necessary to go to this level is if you have a very faint, smudged, or partial fingerprint as your “unknown” and you’re trying to make an identification based on that.
So, while it is probable that identical twins’ fingerprints are more similar than the fingerprints on t-keela’s and Dead Badger’s right thumbs, they are not more significantly different than any two random peoples’ prints from any two of their fingers. It may be the case that t-keela’s right ring finger is just as similar to Dead Badger’s left index finger, as two identical twins’ left thumbs are to each other.
[Sources used in this post: Henry Lee’s “Advances in Fingerprint Technology”, 2nd edition, and lecture notes from my “Fingerprint Science” class.]
