QUESTION OF THE MONTH - May 2019

In the Introduction to his Origin of Species Charles Darwin admitted, "I am well aware that scarcely a single point is discussed in this volume on which facts cannot be adduced, often apparently leading to conclusions directly opposite to those at which I have arrived."

• What directly opposite conclusions could Darwin have meant?
  
  
• How could natural selection inhibit major evolutionary change from occurring on a gradual step-by-step basis?

 

Winning Answer:

Question 1) What directly opposite conclusions could Darwin have meant?

This question has many answers, so who is going to decide the right answer(s)? Anyway, the conclusions directly opposite to those given by Darwin (which is, as we know, that natural variation plus natural selection leads to speciation) must thus be that variation plus selection does not lead to speciation, but to loss of species. This is what Edward Blyth argued and what St. George Jackson Mivart implied. Current biology supports Blyth and Mivart in that (sub)speciation by natural selection is culling the gene pool and leads to specialists, which, as we can see currently happening, are very prone to extinction. So over the long run, species do not appear, but disappear.

Question 2) How could natural selection inhibit major evolutionary change from occurring on a gradual step-by-step basis?

Natural selection is differential reproduction, so any major evolutionary change ocurring in population is inhibited by natural selection when it is not yielding a reproductive advantage, but rather slows down the reproduction rate.

 

More insights from our readers:

Question 1) What directly opposite conclusions could Darwin have meant?

I think Darwin was well aware of the problem, which goes back at least to Titus Lucretius Carus in 50BC. That's why Matthew Arnold was so unimpressed with Darwin, "It's all in Lucretius!" he said. Here's what Lucretius said to a budding materialist who might waver from the faith (book iv)

"In these affairs
We crave that thou wilt passionately flee
The one offence, and anxiously wilt shun
The error of presuming the clear lights
Of eyes created were that we might see; ...
All such interpretation
Is aft-for-fore with inverse reasoning,
Since naught is born in body so that we
May use the same, but birth engenders use:
No seeing ere the lights of eyes were born,
No speaking ere the tongue created was;
But origin of tongue came long before
Discourse of words, and ears created were
Much earlier than any sound was heard;"

So of course Darwin had read Lucretius, and likewise wanted us to banish the thought that eyes were created for seeing and ears for hearing.

Question 2) How could natural selection inhibit major evolutionary change from occurring on a gradual step-by-step basis?

In exactly the same way, Darwin needed progress for blind, purposeless natural selection. On a level ground, a drunk staggering about a lamppost will progress with his average displacement proportional to the square of the time: d = kT². But if the ground is rocky, or sloped, or just really uneven, the progress of the drunk is stopped entirely. Likewise, if natural selection takes place in a smooth, featureless parameter-space (like Dawkins "Mt Improbable") then one might expect a diffusive progress going as time-squared. But none of these things work in the real parameter space of biology. And therefore natural selection, by proof and demonstration, is incapable of progress.