Excerpt from Chapter 2 of Genesis and Genes

Genesis and Genes (Feldheim, 2013) is now available in selected bookstores in Israel, the UK and the USA. A shipment is making its way to South Africa . In the meantime, I intend to post a number of sample passages. Here is a passage from Chapter 2.

***

Human beings have always been interested in heredity. Why does David have his father’s chin, dimple and all, but his mother’s lips? Why do animals and plants so faithfully reproduce their kind, generation after generation? To be sure, offspring are different from their parents, but the differences seem to be limited to a small range of possibilities, so that the defining characteristics of the species are maintained. At least as far back as the ancient Greeks, thinkers have advanced explanations and mechanisms for these phenomena, some more vague and speculative than others.

In the modern era, one of the most influential thinkers in the area of heredity was Jean-Baptiste Lamarck (1744-1829). His comprehensive theory of biology is beyond the scope of this book. What interests us is the fact that Lamarck is credited with the idea that an organism can pass to its offspring characteristics that it acquired during its lifetime (this process is known as heritability of acquired characteristics). The essence of Lamarckian heredity is that an organism’s experiences or behaviour during its lifetime can lead to changes in its physiology which are then inherited by its offspring. The modern conception of heredity is radically different. According to modern genetics, the experiences of biological organisms can never lead to heritable changes. It is genetic mutations – entirely non-teleological and unrelated to the organism’s life experiences – that are bequeathed to the next generation.[1]

The standard example used to explain Lamarck’s approach to inheritance of acquired characteristics is the neck of the giraffe. According to Lamarck, a proto-giraffe stretching its neck to reach leaves high in trees would strengthen its neck muscles. Gradually, as this creature struggled on a daily basis to reach the uppermost leaves, its neck would not only become stronger, but also longer by a tiny amount. Lamarck believed that this physiological change, acquired through the experience of this animal, could be passed on to its offspring, who would be born with slightly longer necks. Extrapolated over eons, the process would result in giraffes possessing the prodigiously long necks we observe them to have. This is how Lamarck himself described the process:[2]

“The giraffe lives in places where the ground is almost invariably parched and without grass. Obliged to browse upon trees it is continually forced to stretch upwards. This habit maintained over long periods of time by every individual of the race has resulted in the forelimbs becoming longer… and the neck so elongated that a giraffe can raise his head to a height of eighteen feet without taking his forelimbs off the ground.”

Sources:

[1] Here is a typical statement regarding the dominant view of heredity today:

Mutation is the central player in the Darwinian theory of evolution – it is the ultimate source of heritable variation, providing the necessary raw material for natural selection. In general, mutation is assumed to create heritable variation that is random and undirected. 

[An environmentally induced adaptive (?) insertion event in flax, Yiming Chen, Robin Lowenfeld and Christopher A. Cullis, International Journal of Genetics and Molecular Biology Vol. 1 (3), pages 038-047, June 2009. The paper can be read here: http://www.acadjourn.org/IJGMB/PDF/pdf2009/June/Chen%20et%20al..pdf. Retrieved 11th July 2011.]

The key point is that heritable variation is random and undirected. It cannot occur in response to an organism’s experiences or environmental pressures, as per Lamarck.

[2] Jean Baptiste de Lamarck, Zoological Philosophy, translated by H. Elliot (1809; translated and reprinted London: Macmillan, 1914), page 122.

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