Since the 1970s, a husband and wife team who are British evolutionary biologists at Princeton University have been studying Galápagos Finches or sometimes they are referred to as Darwin’s finches. In the latest paper by Peter and Rosemary Grant doesn’t show much promise but holds on to a lot of vagueness in testing for evolution.
Since one cannot see the birds actually evolving, fitness is measured. In order to do this, the Grants embraced defining fitness as reproduction, “The fitness of an individual refers to its ability to survive and reproduce” which involves a high degree of complexity to cover all bases in it’s meaning. The problem with this complex definition is that fitness can represent many things including the opposite such as speed or slowness, large size or small as long as more offspring are produced. It can even mean production of large numbers of offspring (as in insects) or very few (humpback whales), and still qualify as “fitness.” The bottom line, whatever is able to survive is deemed to be fit.
They also added another term in their research, “The translation of an individual’s potential fitness into realized fitness is governed by the environment,” but omit the explanation on what differentiates those two terms which makes things a bit confusing. Either an individual survives and reproduces or does not; if it only has the potential to do that, how can anyone measure its fitness until it dies and its offspring are counted?
The Grants attempted to measure what is called, “lifetime fitness” or “recruitment,” which includes measuring relative offspring count at the end of an individual’s life: “Lifetime fitness (recruitment) may be determined solely by producing many offspring, modified by stochastic effects on their subsequent survival up to the point of breeding, or by an additional contribution made by the high quality of the offspring owing to nonrandom mate choice.” All this is saying is how many chicks survive and grow up to pass on the parents’ genes to the next generation.
The Grants mention, “Darwin’s finches deviate from the standard tropical pattern of a slow pace of life by combining tropical (long lifespan) and temperate (large clutch size) characteristics.” Does that mean that what occurs in these finches stays in finches? The Grants conclude…
“Thus, there are two components of biological success, in addition to chance, that have a bearing on the combination of life history traits. The first component is an ability to find food (seeds) in dry years when food is scarce and there is no breeding. The second is an ability to find food (insects and spiders) and avoid interference at the nest from intruders during breeding.”
“Identifying the components, which are two different suites of behavioral and physiological traits, shows where further research is needed to gain a more detailed understanding of how fitness is maximized. Such research may yield insight into the question of how lifespan/reproduction trade-offs evolve differently in different tropical habitats that vary in seasonality, elevation, structure, and climate and also between tropical and temperate zones due to differences in ecology and seasonality, as well as other correlates of latitude.”
So for 37 years of studying these birds, the Grants are unable to narrow down any factor that provides a prediction of upward and onward gains in fitness, whatever that is in it’s high complexity of vagueness in meaning. For all they know from all this time, each one of these factors has oscillated for thousands of years, or else all the birds would have arrived at fitness nirvana by now!