Survival of the what?

December 3, 2006

Pretty much everybody knows the phrase ‘ the survival of the fittest’, but it’s pretty shocking how few people actually understand what it means.

It’s that word – fitness. People don’t get it. It’s not intuitive.

Evolutionary fitness is NOT about physical fitness. It’s NOT about being the biggest and the meanest. It’s NOT about being the smarted or the wealthiest. It’s NOT about being an A-type personality who always wins.

It’s about how many of your genes you pass on to the next generation.

There are lots of ways to do this. You can have lots of children by one mate. You can have lots of children by lots of mates.

Or, and this is actually quite important, you can help your relatives to have lots of children.

There’s a phrase ‘inclusive fitness’ which relates to a value called ‘Hamilton’s R value’. R stands for relatedness.

When you have children they each get half of their genes from you. They are therefore 0.5 the same as you. They are given an R-value of 0.5. If your children grow up and have children of their own, your grandchildren will each get 0.5 of the genes of your children. That’s 0.5 of 0.5 of your genes. So your grandchildren have 0.25 of your genes, so an R value of 0.25.

If you have 2 children your inclusive fitness if 2 * 0.5 = 1.

If each of your children then have 2 children then you get and inclusive fitness of 2*0.5 + 4*0.25 = 2.

On the other hand, if you only have one child, but that child has 10 children, your inclusive fitness is 0.5 + 10*0.25 = 3.

Inclusive fitness doesn’t just work ‘downwards’ to your own offspring, but it also works ‘sideways’ to you siblings.

Your brothers and sisters are given an R value of 0.5 (you do the maths, you each got a selection of 0.5 of each parents genes, but it’s a random 0.5, so you’re likely to share 0.5 of your siblings genes).

If your brother/sister has children, passing on 0.5 of their genes, then each niece/nephew will have 0.5*0.5 = 0.25 of your genes.

So your brother has 3 children, your inclusive fitness is: 0.5 + (3*0.25) = 1.25.

And now a philosophical point

Everyone on the planet is, in some way, related. Therefore if you spend your time helping anyone raise children (for example, by donating to charity to vaccinate children in the 3rd world) your inclusive fitness goes up a little.

The main point

‘Survial of the fittest’ is not an excuse to act like a selfish b*stard. Quite the opposite. If you help people out in life, you get rewarded by increased evolutionary fitness. Think about it.


If you’re interested in writing software, check out my other blog: Coding at The Coal Face

Written while listening to:

Feeling Good by Muse from the album Origin Of Symmetry

Comfortably Numb by Scissor Sisters from the album Scissor Sisters [UK Bonus Tracks]

Drugs by Simple Kid from the album 1


3 Responses to “Survival of the what?”

  1. edarrell Says:

    And in biology, “survival of the fittest” isn’t even about how many genes you pass along — it’s about surviving to pass the genes along. Fitness is judged by whether you survive. Passing the genes along is evidence of fitness, but generally is not the fitness itself.

  2. Dr Herbie Says:

    No, it all comes down to genetics. It’s a matter of simplification. There are many factors to take into account, survival is just one of them, but they all factor down to genes. As I stated in an earlier post, evolution is defined by the genetic makeup of a population. Evolutionary fitness is all about an individuals contribution to that genetic makeup.
    Darwin didn’t know about genetics (although he did posulate a ‘particle of inheritance’) so it seemed to him that fitness was all about survival; it’s all part of the Victorian attitude of nature ‘red in tooth and claw’.
    Sure, survial migh help to increase the number of genes you pass along, but that’s not the whole story. Sexual selection (another term Darwin invented) is also all about fitness, but to nothing to do with survival. If I was to die aged 18, but having fathered 10 children my fitness would be higher that if I lived to 100, but only had two children.
    You may survive a long time, but unless you procreate it means nothing in evolution.
    Neo-Darwinian theory puts fitness down as the number of genes. Dawkins book ‘The Selfish Gene’ was a good spin on Neo-Darwinian theory and shows that it’s really the genes that are surviving, not the organisms.

    I’ll write some more soon about evolutionary modelling and I’ll show that fitness is concerned with both individual survival and an individuals ability to attract mates, both of which translate into the number of genes passed down.

  3. Vesuvius Says:

    I’m ashamed to admit that I had always though of survival in the A-Type personality, megalomaniac sense!

    I stand corrected,



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