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4 Life Evolves
Mendelian inheritance, confirmed and elaborated by Thomas Hunt Morgan who
had by that time been awarded the 1933 Nobel Prize in Physiology or Medicine. It
was a crude job: adversaries occupying themselves with flies rather than advancing
Soviet agriculture were not just fired but jailed. Instead of useless model animals,
Lysenko’s experiments were carried out at a dedicated farm, using cows fed on
chocolate in the hope that their progeny would produce more milk.
Setting these excesses aside, Darwinian and Lamarckian evolution are not always
easy to distinguish. A telling example is the theory of genetic assimilation by Conrad
Hal Waddington (1942). In his experiments, Drosophila were exposed to a toxic
shock of ether, and in later experiments to a heat shock. In response to this, some
flies underwent a phenotypic change (they developed a second thorax), increasing
their tolerance to this environment. After selection for this phenotype for a score of
generations, it was also retained under normal conditions. Waddington was inclined
to interpret this in a Lamarckian way but it can be naturally interpreted as a result
of genetic mutations, similar to adaptation of bacteria in Lenski’s later experiments
(which, however, took many more generations to develop).
Unlike firmly established genetic laws, there are no robust mechanisms for inheritance of acquired characteristics. Only gametes pass genes to offspring, while
somatic cells do not inherit whatever mutations they may accumulate. August Weismann (1885) proved it by cutting tails off white mice for five generations, and seeing
that tails neither disappear nor even grow shorter. However, subtle exceptions, still
unclear, are now being revealed in epigenetics. Some phenotypic (observable, as
opposed to innate) traits are due to operational details of the cells’ chemical plant.
They may feed back on the chemistry of chromosomes and get inherited without
affecting the genetic code itself, but possibly changing the expression of genes by
turning them on or off. Inherited DNA may also be modified in the maternal environment while an embryo develops.
These marginal occasions are not what I mean by Lamarck’s revenge. This comes
when nurture steps in to aid nature. Acquired cultural characteristics are inherited through custom and education by the spreading of memes, a word coined by
Dawkins (1976) in analogy with genes. Throughout human history, memetic inheritance has led to a vast upsurge of complexity in culture and society, while the human
genome has remained virtually unchanged. Yet distinguishing between genetic and
memetic factors is not always easy and is often driven by value judgements. Typically, putting stress on genes is a right-wing, descending to racist, attitude, while
left-wing intellectuals downplay the role of inborn features. A bizarre exception is
Noam Chomsky, notoriously ultra-left on all issues, except those related to linguistics, his profession, where he has been advancing the idea of inborn grammar – of
course, without presenting any proof about how it might be encoded.
Is the progress to complex forms irreversible? Likely yes, save for a major disaster. But human society, becoming more complex in some respects, may get simplified in others. The contemporary societal metabolism in production and distribution
of both industrial and cultural goods is structured in a very complex way. There is a
ladder of national and international bureaucracies, with a cornucopia of regulations,
which only specialists can understand. There is a ladder of corporations, one owning
4 Life Evolves
Mendelian inheritance, confirmed and elaborated by Thomas Hunt Morgan who
had by that time been awarded the 1933 Nobel Prize in Physiology or Medicine. It
was a crude job: adversaries occupying themselves with flies rather than advancing
Soviet agriculture were not just fired but jailed. Instead of useless model animals,
Lysenko’s experiments were carried out at a dedicated farm, using cows fed on
chocolate in the hope that their progeny would produce more milk.
Setting these excesses aside, Darwinian and Lamarckian evolution are not always
easy to distinguish. A telling example is the theory of genetic assimilation by Conrad
Hal Waddington (1942). In his experiments, Drosophila were exposed to a toxic
shock of ether, and in later experiments to a heat shock. In response to this, some
flies underwent a phenotypic change (they developed a second thorax), increasing
their tolerance to this environment. After selection for this phenotype for a score of
generations, it was also retained under normal conditions. Waddington was inclined
to interpret this in a Lamarckian way but it can be naturally interpreted as a result
of genetic mutations, similar to adaptation of bacteria in Lenski’s later experiments
(which, however, took many more generations to develop).
Unlike firmly established genetic laws, there are no robust mechanisms for inheritance of acquired characteristics. Only gametes pass genes to offspring, while
somatic cells do not inherit whatever mutations they may accumulate. August Weismann (1885) proved it by cutting tails off white mice for five generations, and seeing
that tails neither disappear nor even grow shorter. However, subtle exceptions, still
unclear, are now being revealed in epigenetics. Some phenotypic (observable, as
opposed to innate) traits are due to operational details of the cells’ chemical plant.
They may feed back on the chemistry of chromosomes and get inherited without
affecting the genetic code itself, but possibly changing the expression of genes by
turning them on or off. Inherited DNA may also be modified in the maternal environment while an embryo develops.
These marginal occasions are not what I mean by Lamarck’s revenge. This comes
when nurture steps in to aid nature. Acquired cultural characteristics are inherited through custom and education by the spreading of memes, a word coined by
Dawkins (1976) in analogy with genes. Throughout human history, memetic inheritance has led to a vast upsurge of complexity in culture and society, while the human
genome has remained virtually unchanged. Yet distinguishing between genetic and
memetic factors is not always easy and is often driven by value judgements. Typically, putting stress on genes is a right-wing, descending to racist, attitude, while
left-wing intellectuals downplay the role of inborn features. A bizarre exception is
Noam Chomsky, notoriously ultra-left on all issues, except those related to linguistics, his profession, where he has been advancing the idea of inborn grammar – of
course, without presenting any proof about how it might be encoded.
Is the progress to complex forms irreversible? Likely yes, save for a major disaster. But human society, becoming more complex in some respects, may get simplified in others. The contemporary societal metabolism in production and distribution
of both industrial and cultural goods is structured in a very complex way. There is a
ladder of national and international bureaucracies, with a cornucopia of regulations,
which only specialists can understand. There is a ladder of corporations, one owning