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Dictionary of the History of Ideas

Studies of Selected Pivotal Ideas
1 occurrence of Tonelli, Giorgio
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III. GENETICS
  
  
  
  
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1 occurrence of Tonelli, Giorgio
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III. GENETICS

It was an ancient question whether the male or the
female contributes the seed which grows into the em-
bryo; the answer to it partly determined a society's
view of blood-kinship and legal inheritance. In classical
Greece the father was thought to be the primary con-
tributor, but they disputed whether the mother pro-
vides merely nutrition (as in the dramatic decision in
Aeschylus' Oresteia) or a second seed which unites with
the father's. Aristotle's analysis of current theories in
his Generation of Animals shows that discussions were
particularly lively in this field, where much evidence
was quoted, some seriously misleading—for example,
that fishes swallow the milt, or that wound-scars have
been inherited (G.A. I. 17-18, III. 5, IV. 1). He himself
opposed the concept of female seed, but it was ac-
cepted by Galen, Avicenna, and the Renaissance scien-
tists, until finally it was superseded by Von Baer's
demonstration of the mammalian ovum. Among many
diverse theories held by the atomists, “pangenesis”
was important: that seed is drawn from every part of
both parents' bodies, to account for resemblances. An-
other was “preformationism”: that every part of the
embryo must preexist in the seed (“for how could hair
grow from non-hair?” said Anaxagoras). Some argued
that males must develop from the father's seed and
females from the mother's; others attributed sex-
differentiation to differences of heat or position in the
uterus. Multiple births, monstrous growths, superfeta-
tion, sterility, were regularly quoted in evidence: to
some they suggested disproportion between two seeds,
to others they suggested excess or deficiency of heat.

A Persian tradition connecting the semen with the
brain and spinal marrow was followed by those who
held the brain to be the center of psychic activity.
Those who held the heart to be the center argued that
semen must come from the blood. A Greek tradition
associated it with foam (aphros, as in Aphrodite). Aris-
totle rationalized this idea in terms of pneuma, which
emulsifies the semen, being present in it as the vehicle
of soul.

Aristotle gathered together these trains of thought
in a formulation based on his own theory of matter
and form. The male seed transmits soul, which is form
and movement; but its somatic part is sloughed away.
The female contributes only the material (the cata-
menia). Among his arguments, he points out that fishes'
eggs do not develop unless sprinkled with the milt,
yet this does not change them quantitatively; and that
certain insects (as he thought) can receive the male
impulse without a transmission of seed. Using his con-
cept of “mastery” he argues that family likeness de-
pends upon the extent to which the male impulse
controls the female material. Malformations, redun-


232

dancies, sterility, are due to disproportion of materials.

After Aristotle, the concept of female seed was re-
vived by the Alexandrian anatomists, who demon-
strated the genital connections of the ovaries and con-
cluded that these are channels for seeds coming from
the blood. Later Galen demonstrated the oviduct in
sheep; but instead of moving to a concept of mam-
malian ovum, he tried to reconcile this new datum with
Aristotle's view, arguing that the female seed contrib-
utes only nutrition and the allantois, while the male
seed forms the other embryonic membranes (chorion,
amnion) and bodily parts.

It was a universal belief (until Pasteur) that many
insects and plants grow out of rotting materials without
seed. The early cosmologists used this to argue that
life must have begun in that way. A typical account
occurs in the History of Diodorus Siculus in the first
century B.C. In the primeval mud (that is, cold dry earth
mixed with wet rain and the sun's heat) there appear
membranes containing embryo animals of every kind,
which grow up and then reproduce themselves sexu-
ally. There was no ancient theory of evolution out of
simpler forms, and therefore one problem was to ex-
plain how young animals, having appeared sponta-
neously, could survive in the mud long enough to
become mature.

Those like Aristotle, who held that the universe had
no beginning, still had to account for spontaneity. He
argued that pneuma containing vital warmth is some-
times present in water and earth mixed; a foamy bubble
is then formed, out of which may arise eels and certain
of the fishes, testaceans and insects. He would not
however allow that rottenness is a cause, for rottenness
is disintegration whereas only concoction by heat can
generate new life.