Computational Scientific Discovery: Evolutionary Biology

Description

I worked with DePaul Biology professor Ron Edward and DePaul CTI Masters student Raghuveer Kumarakrishnan on a project that compared Evolutionary Biology with Intelligent Design. Supporters of Intelligent Design have stated that life is too complex to have arisen and developed by chance. One example they cite is the development of new traits, which they claim requires simultaneous:

We used the modeling capabilities of the Scienceomatic to test this assertion at face value. Our model considered the interplay of two Mendelian genes with alleles A, a, B and b. All organisms had two alleles of both genes. The genotypes mapped to the following phenotypes which determined fitness:

Genotype(s) Fitness
AABB, AABb, AAbb, AaBB, AaBb, Aabb best
aaBB, aaBb middle
aabb worst
where we imposed the constraint: 
fitness(best) >= fitness(middle) >= fitness(worst)

We then defined 100,000 populations that randomly varied in size, initial percentages of alleles A and B, growth rate, carrying capacity (how large the populations were allowed to grow) and other parameters. In all, our model only made three assumptions, all taken from basic biology:

  1. Logistic growth (that populations tend to grow at an ever decreasing rate as their sizes approach that of their carrying capacity)
  2. Mendelian genetics
  3. The Hardy-Weinberg conditions for allelic equilibrium (minus the assumptions of "sufficiently large population" and "no difference in fitness")

We ran 100,000 models and looked at how allele B (which is never maximally selected for) fares.
Intelligent Design claims it should decrease.
Our model found otherwise. In 57,038 cases the proportion of B increased in the population. Further, a statistical analysis showed that this tendency was more pronounced in smaller populations and for smaller carrying capacities.

Our research shows that all that, contrary to the claims of Intelligent Design, the only requirement for a new trait to become widespread in small but growing populations in geographic isolation. Further, geographic isolation is a reasonable assumption.

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