h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

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So there used to be a lot more diversity, and presumably a much larger human population, until a few thousand years ago, and then some calamity befell mankind and wiped loads of us out?

Hi Dogster,

>Gif: "(Actually, under some circumstances, natural selection can work surprisingly quickly too.)"
>True, but isn't this only the case for very simple changes (like changing the colour of a butterfly's wings)?

It's certainly easier for NS to work rapidly when dealing with changes in existing structures (on a macro scale) or sexually recombining existing genes (on a micro scale). But there is some evidence that entirely new structures can appear within a few generations. See, for example, http://evolutiondiary.com/2008/05/06/lizards-rapidly-evolve-after-introduction-to-island/



>Gif: "A purely evolutionary problem with eugenics is that it leads to a diminution of the (already dangerously small) genetic variation within the human race. This leaves us less variety, and thus less chance of surviving any change in our environment."
>OK, but if you follow this argument through, aren't you saying that millions of people must definitely suffer the consequences of 'preventable' genetic disorders in order that in the unlikely event of a change in our environment that causes most of the population to be killed some would survive?

When it comes to 'disorders' - things like MS etc - it's hard to see any circumstances in which these could be advantageous, no matter what the environmental change (NB: by 'environment', I mean all our surroundings; I'm not particularly talking about climate change), and I'm fully in favour of attempts to get rid of them (though not to the extent of reducing people's rights).

But many 'genetic disadvantages' are conditional - a thick layer of blubber is vital to a seal but fatal to a gazelle. We may not like red hair (*), buck teeth or hairy armpits, but that's not to say that they could never be useful in the future.

More likely, think of a new disease (an 'environmental change') that attacks people with certain genes. Those genes could be anything. Malaria doesn't affect people with the gene for sickle-cell anaemia. Modern crops are notoriously vulnerable to disease because they are monocultures. The last thing we need - from an evolutionary standpoint - is to make ourselves a monoculture.

We are already the only species in our genus; historically, single-species genera are usually the last step before extinction. Groups that thrive are (usually) large, diverse groups where a single environmental change is not likely to wipe out all individuals.

Does that make any sense?

Gif

(*) Actually, red hair is one case where I think more extreme measures are warranted

Hi WG,

Yes, something like that is possible (though you seem to have altered 'tens of thousands of years' to 'thousands of years').

More likely, though, there was no disaster; either we come from a species that nearly starved to death being out-competed on the African plains until we invented tools (a la 2001: A Space Odyssey) or all humans are descended from a single small tribe of a much larger species.

Most other species have no bottlenecks, and in those that do they don't match the dates of the human bottleneck.

Gif

How do we know there was a bottleneck?

Because of numts.

>How do we know there was a bottleneck?<

Because of analysis of mitochondrial DNA, the only kind found in the female ovum.

It appears we are all descended from, I think from memory, 8 original 'Eve' mothers, in the bottleneck.

Sorry that should have been of course, the only kind found in the ovum, outside the cell nucleus. It essentially remains unchanged, not being subject to combining with the sperm DNA.

KZ:

>>If the man is decent he'll do everything he can to support the woman he's got pregnant

Indeed! . Including supporting her in her choice to have an abortion, is this what she wishes. This is what you meant, right?

>>Ed: "Well our decision is was, I guess something to do with the sum of our fears for the difficulties that might be faced by a disabled or ill child minus the joy that can be brought by, say, a child with Downs' Syndrome. (To express it as a formula)."

Dogster:
For that argument to work (mathematically speaking) the potential joys, following your example, of a Downs' syndrome child would have to be larger than the potential joys of a child without.

Except, of course, that one can't actually know. One *assumes* that children bring joy - out bodies seem to want to tell us to have them. And for our part, we couldn't imagine that a child with a disability would bring any less joy. The only thing that mighy have swayed our decision would have been a high risk of gross suffering for the child

As for what you're maybe missing in my argument (except that it's not really an 'argument' , more an expression of a personal choice)...Let's try the argument backwards:
'Why should my wife have taken an amnioscentesis test? What should we have done with a negative result?

Gif:

I know that anti-ginger prejudice seems quite common. Myself - I was surpised to discover it, and didn't do so until well into adulthood. Actually...I have a bit of a thing for redheaded women. (although Women Of Colour tend to score highest on my lust list. )

Ed

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What do you think of people who are dead against the whole idea of abortion because of what it actually is? I'm not talking about angry, placard wavers but just those (of us) who consider that a mother's womb should be the safest, not be the most dangerous, place to be!

mikey

I think that they are entitled to their own fertility choices. I think the choices of other women are none of their damned business. I would oppose any interference in or limitation of that choice. Vigorously.

Effers,

"No birth control is completely different. Women most often have to bear the brunt of childcare and rearing."

So are you saying that the justification for abortion is that it's the lesser of two evils? I disagree. I'm with - I hope I'm right about this - Ed who said that the option to have an abortion is an unalloyed, positive social good, and not just the lesser of two evils.

"It would be good to do a proper scientific survey to actually establish whether there is a higher preference for boys in our culture."

I believe it's been done and in the West there is a small preference for boys. I found this article:

http://www.innovations-report.com/html/reports/social_sciences/report-21717.html

"In the UK (excluding the small percentage of undecided):
16% said they did not care about the sex of their children,
68% said they wanted an equal number of boys and girls,
6% would like more boys than girls,
4% would like more girls than boys,
3% would prefer only boys,
2% would prefer only girls,
16% would prefer a first born boy,
10% would prefer a first born girl
73% had no preference for their first born

"When they were asked what their preference would be if they could have only one child, 19% preferred a boy and 17% a girl: 57% had no preference. The rest were undecided."

and

"He said there was no statistically significant difference between choices given by men and women in the survey, though men slightly preferred boys and women slightly preferred girls."

And related to TRiG's point, this article:

http://www.slate.com/id/2089142/

"Once again, the effect is strong in the United States but even stronger elsewhere. In the United States, Colombia, or Kenya, a couple with three girls is about 4 percent more likely to try for another child than a couple with three boys; in Mexico it's closer to 9 percent, and in Vietnam it's 18 percent. In China, before the one-child policy was imposed in 1982, the number was an astounding 90 percent!"

Gif,

"But there is some evidence that entirely new structures can appear within a few generations. See, for example, http://evolutiondiary.com/2008/05/0...volve-after-introduction-to-island/ "

Wow, that is so totally cool!

"The last thing we need - from an evolutionary standpoint - is to make ourselves a monoculture."

This seems reasonable, but isn't that just setting a bound on the amount of genetic screening or modification we should do?

This may be my ignorance speaking, but how would it happen that we became a genetic monoculture? In agriculture, it's because you always breed from exactly the same starting DNA. I guess in humans the analogous thing would be if we were splicing in some standard pieces of DNA that we knew had some preferred trait (say, intelligence or physical attributes). But would parents want that? I mean, it wouldn't be their DNA that was being passed on then. It would be a bit like choosing adoption over having your own children.

Ed,

"Except, of course, that one can't actually know."

No, but more knowledge means that we can manage the risks we want to take more effectively. I'm not against taking risks, I just like to have some idea of what the chances involved are and what the possible benefits and losses might be.

"Let's try the argument backwards: Why should my wife have taken an amnioscentesis test? What should we have done with a negative result?"

I'm not quite sure how to reply. I'm not saying she should have done, but a reason to do so would have been to know more precisely what the risks were. As to a negative result, it would depend on what that result was exactly.

>>I'm with - I hope I'm right about this - Ed who said that the option to have an abortion is an unalloyed, positive social good, and not just the lesser of two evils.

Dogster. This needs saying. Vigorously.

Of course...*some* think that foetuses shoiuld be safe within their mother's womb. Not god, obviously. Otherwise we wouldn't have the tragedy of miscarriage.

>>"Let's try the argument backwards: Why should my wife have taken an amnioscentesis test? What should we have done with a negative result?"

>>I'm not quite sure how to reply. I'm not saying she should have done, but a reason to do so would have been to know more precisely what the risks were. As to a negative result, it would depend on what that result was exactly.

See...it all comes down to this word 'Risk'. It has various connotations wich are often conflated. One is simply 'probability'. The other is 'a negative consequence'. So I guess that from our point of view, the only thing amnioscentesis might have told us was the probability of an event that we wouldn't have regarded as a negative consequence.

That said...we did find out the sexes of our first two at the scans. Some things are nice to know, I guess. Maybe also it might have been useful to be able to prepare for children likely to have Downs Syndrome...although this can also be detected, later in pregnancy, by ultrasound scans showing the amount of amniotic fluid behind the baby's head.

>So are you saying that the justification for abortion is that it's the lesser of two evils?<

I haven't mentioned abortion at all in this discussion. But I will now. I'm full agreement with Ed about it. For many of the reasons I gave for birth control, abortion is equally valid. A woman musthave the right to choose as they are the ones that carry the child, and risk emotional attachment therefore, possible leading to all sorts of negative consequences for them, for their whole life if they are not given the option of 'termination'.

I'm getting a bit tired of your overly theoretical stance, and seeming lack of awareness of the practical realities of many women's lives in the present, all over the world; to a lesser degree admittedly, here in the present. But the past has been hellish for many women because of these issues. The fight to improve things has been long and hard, and is still not won. I'm not whinging about that; just stating fact.

Effers,

"I haven't mentioned abortion at all in this discussion."

Oh I was kind of including abortion in birth control. Is that not right? I'm not sure how people use the term.

"I'm getting a bit tired of your overly theoretical stance, and seeming lack of awareness of the practical realities of many women's lives in the present..."

I don't understand why you're being so hostile. What have I said that makes you think I'm so unaware? I'm talking about it in this overly theoretical way because I want to get to the bottom of something that has puzzled me for a long time - the moral case for why at an individual level parents shouldn't choose the sex of their child, rather than the ethical case for why a society shouldn't allow parents to choose the sex of their child. These two issues are separate, but people only ever talk about the latter.

>I don't understand why you're being so hostile.<

>"I'm getting a bit tired....<

You call that me being hostile, Dogs......

I'm impatient that so many men just don't see that equations, logic, reason amount to nothing more than a hill of beans when it comes to the way issues are discussed about harsh practical reality. The hard evidence. The best teacher of all.

Were we to have this same discussion in a 100 years time, I optimistically hope it would make more sense, and I would be less mildly irritated with you, because the issues would have become neutral in a sociolgical sense.

Revolutionary types like me always end up getting a bit impatient with idealists and theorists when it comes to the hard realities of real life, and all the power structures in place that make certain issues any thing other than neutral.

Ed,

"the only thing amnioscentesis might have told us was the probability of an event that we wouldn't have regarded as a negative consequence"

It might have told you that there was "a high risk of gross suffering for the child" though?

Here's another point of view. I agree that you can live a perfectly happy and fulfilling life with a disability, but isn't it better not to have one even so? I can have a perfectly happy and fulfilling life as I am, but I'd love it if I had the ability to fly. Maybe this is it then, that you can think of having a disability (being blind say) as being similar to not having the ability to fly - not something that we should get worked up about. But is that really true? I mean, doesn't one suffer as a consequence of not having an ability that everyone else has? Is it then just a question of the degree of suffering involved?

Somewhat related: how do people feel about this?

http://www.usatoday.com/tech/science/genetics/2006-12-21-designer-disability_x.htm

To summarise, it's the suggestion of genetic screening to ensure that a child IS born with a disability. I think to most people, this would seem somehow worse than the idea of screening to ensure that a child is born without. Is this just because most people aren't disabled and so haven't experienced that life and instinctively fear it as alien and other? Or is there something more to it?

I wonder if people are against things like sex selection because of some idea that it's not natural. Personally, I'm deeply, deeply uninterested in whether things are natural or not. As a famous incident on this thread should remind us, talk of whether things are 'natural' or not is often just a cover for socially conservative thinking, and I think most of the atheists here would agree with that. One of the reasons for my bringing these questions up on this thread is that it's interesting to discuss them with a bunch of atheists who don't have superstitious notions about morality.

The other thing I wonder about is whether or not people don't like the idea of selecting for particular attributes in children because they think it reflects something about them rather than about the children. That is, if you were blind you might object to someone else selecting for children that can see because you think that by doing so they are somehow attacking you.

Oh, and please feel free to criticise me as strongly as you want if you think I'm saying something objectionable. I realise that the view I'm putting forward here is one that a lot of people would disagree with.