Acquired Characteristics

The features of a living thing which are not inherited. The view of evolution attributed to Lamarck (earlier espoused by Erasmus Darwin) was that the acquired characteristics like a blacksmith's brawny arms were inherited by the blacksmith's children, so that the term often appears as ''the inheritance of acquired characteristics''.
In a way, this simple belief is easy to understand: blacksmiths were probably naturally brawny to begin with, and if their children were trained to the forge, then they, too, would develop significant muscles, but only because they had inherited their father's genes and trade. It was and is an attractive belief, because it suggests that the efforts of the parents to improve themselves may not be entirely wasted. sadly, attractiveness is not a key requirement for scientific theories.

The Lamarckian legend has it that Lamarck suggested that giraffes wanted (wished for) longer necks, their necks grew, and the longer necks were then inherited. In fact, Lamarck suggested that the giraffes had a want (a need) of longer necks, and that longer necks were inherited. In a sense, he was quite close to the Darwinian view of variability occurring in nature, with some variants being more successful than others.

The classical experiment refuting the inheritance of acquired characteristics is probably to be found in the need for certain cultures to continue circumcising their male offspring, and Charles Darwin recorded that in the Muslim Celebes (Sulawesi in modern Indonesia, boys went naked up to the age of six or seven, and a correspondent had assured him that the prepuces of boys there were noticeably shorter, circumcision being a later operation than is the Jewish practice.

A more formal experiment was carried out by August Weismann (1834 - 1914), who cut off the tails of mice through 22 generations, but obtained no shortening effect in the offspring.
The other ''experiment'' carried out on this effect is the celebrated ''case of the midwife toad'' the studies undertaken by Dr Paul Kammerer, which ended when he took his life in 1926. Born in 1880, Kammerer was well-known as a biologist in Vienna who was immensely skilful in breeding amphibians. One of these involved the two European salamanders, Salamandra atra, an alpine species, and Salamandra macujosa, found in the lowlands, which produces tadpoles, unlike the alpine species.

Kammerer apparently managed to demonstrate that the lowland species, bred under alpine climatic conditions, produced live metamorphosed young, while the alpine species in lowland climatic conditions, produced tadpoles after several attempts. More importantly, the changes became more pronounced after several generations.

Then came the work with the midwife toad Alytes obstetricans, which mates on land. The male load grips the female (amplexus) and holds on until the female lays eggs in water, and the male then covers these with sperm. For those species mating in water, the male grips the slippery female with small horny spines, called nuptial pads. The midwife toad mating on land, does not need these pads. Kammerer reported that when the midwife toad was forced to mate in water, the males, over several generations, developed nuptial pads.

After many years' breeding, the strain of toads died out during the disruptions caused by the First world war, and one surviving male was preserved. One of the pads was converted into microscope slides, the other survived on the preserved specimen. when this specimen was shown to have been injected with Indian ink to produce the ''pad'', a scandal broke out, leading to Kammerer's suicide.

To this day, nobody knows who did the injecting. Some suggest Kammerer was a simple fraud, others suggest that an assistant may have ''touched up'' a fading specimen. The best available account is in a book by Arthur Koestler, called The Case of the Midwife Toad. The doctrine of inheritance of acquired characteristics was popular in Stalin's Russia, and the story of Kammerer was made into a propaganda film called Salamandra.

Written by Peter Macinnis


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