Academic journal article Mankind Quarterly

The Role of Niche Construction in the Evolution and Future of the Human Brain

Academic journal article Mankind Quarterly

The Role of Niche Construction in the Evolution and Future of the Human Brain

Article excerpt

The author discusses the phenomena of niche construction in the evolution of the human brain, and explores the relation between culture and environment and how this relation can effect changes to the geometry of a species niche.

Feedback pressures resulting in an increase in brain size are discussed, along with the idea that the development of a caste system, involving selective mating and 'in-mean-trait' reproduction, constitutes a potential inhibitor to subsequent brain size increases.

Finally, the future of the human brain is discussed in the context of eugenics - the apex of Homo's ability to niche construct - and the likely effects of contemporary cultural changes on the future of the human brain.

Key Words: Human ethology; Niche construction; Caste system; Eugenics; Genetic inheritance; Cultural Inheritance; Ecological inheritance; Gene-culture co-evolution.

Niche - An Ill-defined Concept

Three major attempts were made at defining the concept of the ecological niche in the 20th century.

The first was by Joseph Grinnell in 1917. Grinnell proposed that the niche was a recess or region within an environment that combined both species habitat and nutritional requirements. His conception of the niche was one where it could be differentially occupied and vacated by organisms possessing similar life styles. The niche of Grinnell owed nothing to the activities of the organism it contained. It existed as a largely immutable entity, prefabricated by the environment subject to change only by the environment (Grinnell 1917, 1924, 1928).

The second definition of niche came from Charles Elton in 1927. He envisaged the niche as being essentially where an organism was in relation to other organisms in a food chain or web. The niche in this respect was defined by other species rather than by the environment. If extinction occurred at the terminals of a food chain, then theoretically a species with similar trophic characteristics could come to occupy the vacancy (Elton 1927).

In comparison, Grinnell defines what is essentially the species 'address' within an ecosystem, i.e. where it can be found, whilst Elton describes the species 'profession', i.e. what it does within its ecosystem. As abstractions these definitions sufficed for 20 years, but it was their lack of quantitative character that in part, prompted George Evelyn Hutchinson to develop his breakthrough concept of the niche in 1944. Hutchinson envisaged the niche as being comprised of many dimensions, each of which corresponded to an environmental factor acting on a species. These factors could be represented as axes of environmental or resource gradients on a multivariate graph. Species could be illustrated as degrees of distribution along each of these gradients. For each new factor, another axis could be added to the graph. Niches in this picture become multidimensional hyper-volumes. Hutchinson suggested that the region of a species niche that was free of other species, i.e. not partitioned, is the realized niche, and the total volume, including that which is shared with other species, is the fundamental niche (Hutchinson 1944, 1957).

Hutchinson's niche is considered to center around the species it contains, so according to the Hutchinsonian definition of niche, it is not possible to have an unoccupied niche as it is defined by the distribution of species along environmental gradients, although this particular interpretation has been challenged (Woodley and Sikes 2006). For an exhaustive discussion of the history of the niche concept, see Schoener 1989.

Niche Construction

Because species are capable of modifying their environments around them to varying degrees, they are capable of modifying the niches that contain them.

This process could theoretically lead to a change in the selective pressures acting on those species over time. This is the central argument of Odling-Smee et al (2003). …

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