Waiting on Darwin


"To the extent that waiting time is a serious problem for classic neo-Darwinian theory, it is only reasonable that we begin to examine alternative models regarding how biological information arises." -John Wakeley

The waiting time problem in a model hominin population is a theoretical problem in evolutionary biology that concerns the time it takes for a beneficial mutation to become fixed in a population. The problem arises because the probability of a beneficial mutation occurring in a single individual is very low, and even if it does occur, it may take many generations for that mutation to become widespread in the population.

In a 2003 paper, John Wakeley and colleagues used computer simulations to investigate the waiting time problem in a model hominin population. They found that the waiting time for a beneficial mutation to become fixed could be very long, even under optimistic assumptions about the mutation rate and population size. For example, they found that a beneficial mutation with a fitness benefit of 10% would have a waiting time of about 10 million years in a population of 10,000 individuals.

The waiting time problem has implications for our understanding of human evolution. It suggests that the evolution of complex traits, such as bipedalism or language, may have taken much longer than previously thought. It also suggests that some of the traits that distinguish humans from other animals, such as our large brains, may have arisen as a result of random genetic drift, rather than natural selection.

The waiting time problem is a complex problem, and there is no single solution. However, the work of Wakeley and others has helped to shed light on this important problem in evolutionary biology.

Here are some of the key findings of the study:

  • The waiting time for a beneficial mutation to become fixed can be very long, even under optimistic assumptions about the mutation rate and population size.

  • The waiting time problem is more severe for complex traits that require multiple beneficial mutations to occur.

  • The waiting time problem can be mitigated by increasing the population size or the mutation rate.

The waiting time problem is a significant constraint on the evolution of complex traits. By understanding the factors that affect waiting time, we can better understand how complex traits evolve and how they can be selected for in a population.

Article snippets:

Biologically realistic numerical simulations revealed that a population of this type required inordinately long waiting times to establish even the shortest nucleotide strings. To establish a string of two nucleotides required on average 84 million years. To establish a string of five nucleotides required on average 2 billion years

However, even using the most generous feasible parameters settings, the waiting time required to establish any specific nucleotide string within this type of population was consistently prohibitive.

We show that the waiting time problem is a significant constraint on the macroevolution of the classic hominin population. Routine establishment of specific beneficial strings of two or more nucleotides becomes very problematic

Yet in this paper we show that in a small mammalian population it is not generally feasible to even establish a string of five nucleotides, not even in a billion years.

Our studies show that in such a population there is a significant waiting time problem even in terms of waiting for a specific point mutation to arise and be fixed (minimally, about 1.5 million years

We show that the waiting time problem becomes very severe when more than one mutation is required to establish a new function

We show that the waiting time problem becomes more extreme as string length increases, as fitness benefit decreases, and as population size decreases. In a population of 10,000 the establishment of a string of just two specific co-dependent mutations tends to be extremely problematic (conservatively requiring an average waiting time of at least 84 million years).

For nucleotide strings of moderate length (eight or above), waiting times will typically exceed the estimated age of the universe – even when using highly favorable settings.

Many levels of evidence support our conclusions, including the results of virtually all the other researchers who have looked at the waiting time problem in the context of establishing specific sequences in specific genomic locations within a small hominin-type population

To the extent that waiting time is a serious problem for classic neo-Darwinian theory, it is only reasonable that we begin to examine alternative models [39, 40] regarding how biological information arises.


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