This past December, science writer David Dobbs published an essay (2013) in the online magazine Aeon (aeon.co/magazine/) that purports to explain why the ‘selfish gene’ concept is outmoded and should be retired. It elicited a good deal of commentary, and in early March, Aeon published responses (Sapolsky et al., 2014) to the original article from four individuals (two scientists, a genetic counselor, and a philosopher) as well as additional comments by Dobbs. For those who are interested in this controversy, responses to the original Dobbs article were also posted elsewhere by Richard Dawkins (2013) and Jerry Coyne (2013a, b). Below, I provide a sense of the arguments of Dobbs, the tenor of the criticisms of Dobbs’s piece, and selected other critiques of the gene-centric approach to evolution. (more…)
In his 1987 book, “The Evolution of Individuality,” Leo Buss addressed a fundamental biological question: “How could individual multicellular animals (known as metazoans), like sea anemones, insects, frogs, and humans arise?” Buss focused on a key challenge confronting any multicellular animal with differentiated cell types performing different functions: the potential conflict between selection on the whole organism and selection on the cells that constitute the organism (or on the whole genome and the individual genes that constitute the genome). A new study (Dejosez et al., Sciencexpress, 2013) explores this issue by using a genome-wide screen to identify genes that favor cell cooperation and discourage so-called “cheater” cells that through genetic or epigenetic variation outcompete wild-type cells in the developing embryo. (more…)
In the book, The Winner-Take-All Society (1995), Robet H. Frank and Philip J. Cook discuss a hypothetical scenario in which a new genetic technique allows babies to be engineered so that they have a 99% chance of performing 15% better on the standardized tests used in American college admissions, such as the Scholastic Aptitude Test (SAT) without actually being smarter in other contexts. In 1% of babies so engineered, a severe emotional disability will result. Frank and Cook speculate that many parents would be willing to risk the odds that an enginnered child would not be among the 1% of offspring who suffer the ontogenetic costs of the procedure. They further argue that as more people exploit this genetic modification, the emotional pressure on the hold-outs would increase. (more…)
Natural selection depends on heritable phenotypic variation. The most obvious source of phenotypic variation is genotypic variation. A new study, by Casanueva et al. in Science (2012) suggests that in addition to genotypic variation, variation in life history and stochastic variations in gene expression can substantially affect phenotypic variation.
These authors studied mutation penetrance in Caenorhabditis elegans overexpressing a transgenic transcription factor (heat shock factor 1 or HSF-1) that controls the expression of genes encoding proteins that are involved in stress responses. The worms expressing high levels of the HSF-1 transgene (hsf-1) were previously shown to be better able to cope with diverse environmental stresses than otherwise identical worms not expressing the HSF-1 transgene.
Casanueva et al. then crossed HSF-1 transgenic worms with worms that harbored a variety of mutations that affect embryonic or post-embryonic development . In the majority of these crosses, the overexpression of HSF-1 was associated with reduced penetrance of these genetic variants. (more…)
A minimal requirement for evolution via natural selection is heritable phenotypic variation that affects reproductive success, or more generally, genetic success. The concept of heritability is often used somewhat loosely in casual non-technical conversation, but there is also a precise technical definition – actually there are two widely-employed technical definitions, each of which is characterized below.
Consideration of the meaning and usefulness of heritability is prompted by the publication of a new study (Hallmayer et al., 2011) addressing the relative contributions of genetic and environmental variation in the origins of autism. (more…)