Tuesday, January 10, 2012

Fascinating Evo Biology lecture

Anna Dornhaus gave an interesting lecture on evolutionary biology. I really like this thread ever since I read The Selfish Gene but am finding the stories repetitive, so these were all fresh. Here's some of her stories.

Warblers are very good at detecting which of their eggs are cuckoo eggs, something that is not detectable from a casual glance. Cuckoos know they have to at least remove one of the Warbler eggs before adding their own, so the competition is clearly into overdrive. Yet, occasionally the Warblers are fooled into letting the Cuckoo egg stay, and once hatched the Warbler raises the behemoth Cuckoo even though it looks nothing like its siblings (3 times the size, different color). It seems conscious minds can only afford to be so discriminating in certain areas, the rest apply simple rules.

Minds aren't good at detecting things that never happen in nature. Omnivores like rats are good at figuring out what foods are not good for them, using the simple rule that if they get sick, anything they ate 2 hours ago is no longer considered tasty. Vampire bats only drink blood, and as blood is basically never poisonous, if you do poison the blood to make the bats sick, they will never associate it with the blood from that source. They can't make the connection because from an evolutionary perspective, it basically doesn't happen.

Different species of sticklebacks live in the bottom and top of lakes. The top-dwelling sticklebacks can't learn landmarks. It appears the bottom dwelling fish are very good at detecting landmarks, while the top-dwelling fish looks more at how things behave. So perhaps skills not useful in their evolutionary past are eventually lost. On the other hand, female birds are not very good at remembering where they stored food when they have mated because they rely on their mate. Unmated females, however, are just as good as the males at remembering seed caches. I imagine one could therefore argue top-dwelling sticklebacks failed their spatial geometry quiz because it had no value to them.

Some animals grow the brain during the part of he year they need it more, and then lose that in the part when they are less cognitively demanding part of the year. More evidence for the use it or lose it principle.

Interestingly, scientists bred fruit flies for intelligence. They made bananas taste bitter, which fruit flies don't like. They then gave the flies little markers, so the 'smart' ones would avoid the bitter bananas based on this learned signal, the dumb ones would not. After only 20 generations they generated 'smart' and 'dumb' fruit flies who could learn at different success rates. Then, they mixed them together and saw what happened: Idiocracy, the dumb flies out-reproduced the smart ones! Her take-away was intelligence is costly, and everything has trade-offs.

I especially like the idea that any ability comes with trade-offs and so in a sense we are all idiot-savants, good at some things, bad at others, especially with respect to really different people. I know a lot of smart people, but I've never met one who didn't have blind spots. It's good to remember that because if you think that because you have a really high IQ, are really rich, or are a good speaker, you are therefore the smartest guy in any room, you are going to make a very big mistake someday.


Anonymous said...

I second the idea of trade-offs. I keep telling this my students.

It is even more important on the population level: all qualities come as distributions and it is reasonable to assume that during evolution the distribution of characters in a population already represents an optimized set. In other words it is unlike any kind of eugenics will improve the performance at the population level. Basically, the idea of eugenics is naive both on the individual and on the population level.

There is a related issue, which is the question whether "success" at any one point in time means much for success in "the future". Individuals or populations that are currently "successful" (Darwin's "favored races", sic), are well adapted to current conditions. This says nothing about how well they would fare under some different living conditions. Once again, the long term averaging that evolution has done already is to be trusted more that some optimization based on current short terms trends. -mbk

Dipper said...


highly recommended

Christian said...


When you speak of optimisation I wonder if you aren't bundling together two concepts.

When you describe the result of an evolutionary selection as optimised (or close to it) it becomes tautologous, and all you mean by an optimised distribution is one that results from that selection, by definition.

The less specialised meaning of optimisation implies some sort of evaluation against a standard which may well be other than mere survival.

Our urge to use our minds to make choices about aspects of our environment that we wish to adjust to secure our survival is an evolved feature of our species. "Current conditions" are the product of our cultural choices in this matter, and we seek to create ones that secure our survival and our values.

Refusing to choose to evaluate evolutionary outcomes against our values seems like its own sort of choice. It's a choice of fatalism and nihilism and a denial of an important aspect of our natures as creatures that evaluate and find and confer meaning on the world. It is a denial of our humanity.

In practice it describes a life that cannot be lived without illogic and inconsistency - if you hold a value then must promote it, and if you don't then there is another higher value that weighs heavier. Isn't their an implicit principle of reverence for non-engineered outcomes in your refusal to choose any other human standard by which to evaluate evolutionary outcomes?

If female education reduces women's fertility it would seem to reduce their evolutionary fitness (and their society's fitness). We live in a world where willy-nilly we are selecting against women who have the aptitude and interest in being educated, to the extent that this is heritable (IE a large extent: see JR Harris The Nurture Assumption 1998 et al). If we don't choose to counterbalance this effect, do we not choose to accept it? Do we not choose to drive women back into an imprisonment within a biological destiny that is actually no longer a destiny precisely because we can choose something else?

Kilbourn said...

Very interesting, but is there actually any application to human societies? Male intelligence is a universal sexual attractor for human females (typically expressed in social acuity rather than book smarts, bare in mind), and the type of mating system a specie employs obviously has a strong influence on who reproduces successfully. Could there be any overlap whatsoever between humans and flies, whose less social nature obviously calls for different biological traits?