A peer-reviewed paper published towards the end of last year in the Elsevier journal Progress in Biophysics and Molecular Biology has a provocative title: “Neo-Darwinism Must Mutate to Survive.” The paper’s abstract opens with points that few would dispute:
Darwinian evolution is a nineteenth century descriptive concept that itself has evolved. Selection by survival of the fittest was a captivating idea. Microevolution was biologically and empirically verified by discovery of mutations.
However, there then comes a major “but”:
There has been limited progress to the modern synthesis. The central focus of this perspective is to provide evidence to document that selection based on survival of the fittest is insufficient for other than microevolution.
And according to authors Olen R. Brown and David A. Hullender, just what is the basis for saying this? It’s calculations showing that the likelihood of microevolutionary processes adding up to macroevolutionary changes is highly improbable:
Realistic probability calculations based on probabilities associated with microevolution are presented. However, macroevolution (required for all speciation events and the complexifications appearing in the Cambrian explosion) are shown to be probabilistically highly implausible (on the order of 10-50) when based on selection by survival of the fittest. We conclude that macroevolution via survival of the fittest is not salvageable by arguments for random genetic drift and other proposed mechanisms.
They go on to state, “We are critical, as previously explained, of the position that macroevolution is sufficiently explained by the processes useful for microevolution — in particular that mutations and survival of the fittest are adequate to the task,” and argue that “Microevolution does not explain speciation — only smaller changes.”
A Familiar Critique
Prior to the publication of this paper I was not familiar with these authors (though Olen R. Brown contributed an article to Evolution News while I was in South Africa completing my PhD). But clearly they share a critical perspective on neo-Darwinism that is very similar to that of the intelligent design community. Consider this striking passage:
Survival of the fittest is adequate to select for such changes (gains) which occur within one genome primarily by single fixed mutations (and perhaps sometimes by horizontal gene transfer). Macroevolution, however, requires major changes necessitating multiple changes that logically most frequently occur in multiple genomes. Therefore, the concept survival of the fittest is inadequate to conserve individual changes in multiple genomes where the individual changes generate no increased fitness. … Thus, survival of the fittest is illogical when proposed as adequate for selecting the origination of all complex, major, new body-types and metabolic functions because the multiple changes in multiple genomes that are required have intermediate stages without advantage; selection would not reasonably occur, and disadvantage or death would logically prevail.
What they are saying is that when some feature requires multiple changes before providing an increase in fitness, the changes cannot be produced by mutation and selection alone. Their subsequent comments, read carefully, almost sound like an implicit endorsement of intelligent design:
It is our perspective that the burden is too great for survival of the fittest to select evolutionary changes that accomplish all evolutionary novelty. Thus, evolution lacks a sufficient mechanism for multifactorial selections because a process that looks forward, is nonrandom, deterministic, or occurs by an unknown biological process, is required. The position of mainstream biologists regarding this aspect of evolution is that nature is always non-purposeful and, therefore, the proposed selection (process, force, tendency), could not possibly be natural (scientific). However, our perspective is that this is a supposition of necessity rather than an established principle. Logic demands that it be open to investigation. This first requires an openness to ideas and science must be open to new ideas.
They thus propose that evolution is only possible if it is “nonrandom, deterministic, or occurs by an unknown biological process” — something that some would reluctantly conclude “could not possibly be natural.” They continue:
Darwin wrote in On the Origin of Species… : “If it could be demonstrated that any complex organ existed, which could not possibly have been formed by numerous, successive, slight modifications, my theory would absolutely break down. But I can find out no such case.” Today, Darwin’s missing cases are abundant including each complex transition to a new body type, metabolic cycle, or metabolic chain. Multi-step processes are routinely required at every evolutionary step.
They then perform a probability calculation which shows that the likelihood of producing a necessary pathway would require such multi-step processes leading to probabilities below the plausibility bound they had previously set.
Origin of the Krebs Cycle
They use a case study of the origin of the Krebs cycle — a metabolic pathway involving 12 enzymes that is necessary for life. They believe that this is a useful test for evolution. They assume that the genome is “ripe” to produce each enzyme where a minimal number of mutations is needed for a gene to suddenly become functional. They therefore choose an incredibly generous value of 0.00001 as the probability that a given enzyme can be created by a single mutation.
They calculate the likelihood of producing all 12 enzymes needed to produce a selectable function as 10-51. They note this is below 10-50, a probability that was called “negligible” by Émile Borel, the French mathematician, who stated “this process of evolution involves certain properties of living matter that prevent us from asserting that the process was accomplished in accordance with the laws of chance.”
They also reject co-option and exaptation as possible explanations for the origin of the Krebs cycle:
The idea that the complete, functioning Krebs cycle arose by purloining each intermediate step from other uses (Meléndez-Hevia, 1996) lacks empirical support. The discoveries that genes can be switched on and off, that codes read forward and backward, gene duplication, and the homeobox, are helpful but inadequate to save evolutionary theory without modification.
In the end, producing a complex feature like the Krebs cycle is just too improbable because “Selection based on survival of the fittest, for anything beyond single mutational changes in a genome, is insufficient scientifically and biologically.” They conclude, “there is something besides mutations and survival of the fittest needed to explain evolution.”