Genetics and Kin Selection

[pErvinalia]

I drank too much over Christmas, I've just woken up after a couple of hours sleep in the late afternoon (and therefore barely know what century it is, let alone where I am), and I haven't had any Valium today to clear out the noise. So I want someone to do the maths for me and then to explain how kin selection stacks up.

A quick google search brought up a Scientific American article mentioning that humans on average share 99.9% of genes with each other. So you and your partner get together and make a child which shares 50% of each parent's genes. So we'd expect the child to share 99.95% of genes with each parent, if my mathematical logic is correct. So how do we get from a 0.05% (i.e. a tiny bloody amount) increase in your direct descendent's genes compared to any other random human, and throwing ourselves under a bus (etc) for that child? It's such a tiny amount that it barely makes any sense protecting our progeny in comparison to protecting any other random human. But given that it does actually happen, it's pretty amazing that such a tiny amount can lead to us feeling such strong protective emotions over our close relatives. Just doing another quick google search it seems we have 20-25k protein encoding genes. Which works out to about 12 genes difference between your child and any other random human. CRAZY!

What's going on?

Therefore God?

[Tyrannical]

They now say 99.5% similar instead of 99.9%, and that's on average. If you were comparing two members of different ethnic groups, the similarity would be again less than 99.5%
Further differences are caused by gene expression, which is basically genes being turned off and on and how cells uses the genes instead of being caused by differences in the dna.

[pErvinalia]

But the parent can't be aware of which genes are turned on or off. So if we work on 99.5% (where did you get this figure?), then there is a 0.25% difference between your child and any other random human. We are still talking only 63 genes at max.

[Tyrannical]

But the parent can't be aware of which genes are turned on or off. So if we work on 99.5% (where did you get this figure?), then there is a 0.25% difference between your child and any other random human. We are still talking only 63 genes at max.

You can be aware of what genes are turned off sort of, it can affect everything from physical looks to behavior to susceptibility to disease.
That 99.9% went away at least ten years ago, common google searches come up with the 99.5%.
That 63 genes sounds like you were only looking at protein encoding genes when you did your math, that's only about 1.5% of the genome. Not sure what just the protein encoding variability is in humans.

I can't seem to find it through a quick google search now, but I seem to recall that with epigentics average human variation is around 89%. But small differences can make big differences, just look at how much human variability there is both physically and behaviorally.

[pErvinalia]

Non protein encoding genes are either useless or shared by virtually all life on the planet. I don't think they are relevant to this.

[Tyrannical]

Non protein encoding genes are either useless or shared by virtually all life on the planet. I don't think they are relevant to this.

Nope, there is a lot of human variability in these also and they are important. Some of them (but not all) have been previously called junk DNA, but even some of thought is believed to be important. That human genome project wasn't the end, it was just the beginning

[pErvinalia]

I thought the non "junk" ones were the genes that all life on the planet shares. At the very least it would be shared by all animals.

[pErvinalia]

I might do me some genetic reading over the next few days. Been 20+ years since I last studied any genetics.

[Tyrannical]

Fun fact, after about 8 generations of decedents (great great great great great grandparent) there is a 50% chance you share no DNA with that ancestor.

[pErvinalia]

Thinking back, I wonder if a source of significant variation are alleles of the particular genes?

[JimC]

From the point of view of the selfish allele, if the behaviour of the lumbering biological robot it has constructed assists the spread of its identical copies elsewhere by even a small amount, then that behaviour will become the norm.

[pErvinalia]

If alleles lead to a significant difference. If not, then a tiny percent difference is incredible that it can cause such large behavioural changes. I reckon it's probably a case of alleles and epigenetics (as T said). Families probably share similar epigenetic traits, much more so than other random individuals.

[JimC]

If alleles lead to a significant difference. If not, then a tiny percent difference is incredible that it can cause such large behavioural changes. I reckon it's probably a case of alleles and epigenetics (as T said). Families probably share similar epigenetic traits, much more so than other random individuals.

A tendency to help/protect closely related people could be triggered by very simple cues (for example olfactory, or simply close association) would not require highly complex genetics to be inheritable - it is simply adding an "if that, then this" trigger.