Reply to Haldane 1594 Chicken and Egg
Which came first, the chicken or the egg? I am here indebted to a witty
discussion note by Roger Teichmann.^21 Since each chicken is hatched from
an egg and every egg is laid by a chicken, it would appear that neither can
come first. On the other hand since the durations of the generations of
chickens have a lower bound (so the sequence is not like, say,...^1 / 8 ,^1 / 4 ,^1 / 2 ,
1,... ) and because life on earth has not existed for ever, it would appear that
there would have to be a first egg or first chicken. The answer of course must
be that ‘chicken’ is a vague term. We get the same appearance of contradiction
with any vague term, as is exemplified by the so-called Sorites paradox. If
a man with only a few hairs on his head (say 10) is bald, so also is a man with
one more hair (say 11). Also if a man with n hairs on his head is bald so is
a man with (n+ 1) hairs. (One more hair does not make the difference
between being bald and being not bald.) So from this we seem to be able to
deduce that the hairiest head of hair that you’ve ever seen is that of a bald
man. Much has been written on the Sorites paradox, and as far as I know
there is still no agreed solution. The trouble comes from the vagueness of
language, as with ‘bald’. Similarly ‘chicken’ is vague. There is no first chicken.
Species evolve imperceptibly from earlier species. Unless, of course, some
miraculous occurrence singled out a first chicken or a first egg.
We should take ‘egg’ here in the sense of ‘ovum’. (The eggs we eat consist
mostly of nutrient for the growing chicken foetus.) Wouldn’t there have to be
a first ovum? Well, there might have been a first coming together of bits of
DNA to form the first prototype of bisexual reproduction, and one of them
might be regarded as proto-egg and proto-sperm.
Haldane likes to stress the discontinuities: the reproductive from the non-
reproductive, the organic from the non-organic, the conceptual from the
non-conceptual.^22 These things arise by sequences of small jumps. Each jump
may have a low probability, but evolutionary time is long compared with the time
of human affairs. If a jump consisted simultaneously of millions of jumps
its probability would be exceedingly low. However, a sequence of millions
of small jumps filtered by natural selection can have a much higher probability.
There is a problem about how the evolution of a complex organ, such as the
eye, might have occurred. The answer lies in the opportunist character of evo-
lution whereby something that gives one sort of advantage at one stage may
lead to different advantages at later stages. Haldane might say that small jumps
are still jumps. So they are, but the smallest jumps are a matter of chance
comings together and chance mutations. But you shouldn’t be reading me on
this. Read the biologists and make up your own mind whether you think that
the naturalist story or the supernaturalist story is the more plausible.