The Evolution of Evolution 103I well remember how the synthetic theory beguiled me with its unifying power when
I was a graduate student in the mid-1960’s. Since then I have been watching it slowly
unravel as a universal description of evolution. The molecular assault came first, fol-
lowed quickly by renewed attention to unorthodox theories of speciation and by chal-
lenges at the level of macroevolution itself. I have been reluctant to admit it—since
beguiling is often forever—but if Mayr’s characterization of the synthetic theory is
accurate, then that theory, as a general proposition, is effectively dead, despite its
persistence as textbook orthodoxy. (Gould 1980b:120)As the full quotation clearly shows, Gould is talking about the neo-Darwinian synthesis and
is not expressing doubts that evolution occurred. Creationists either can’t tell the difference
or are deliberating misquoting Gould to mislead their readers.
Now that we have cleared up the creationist misunderstanding that a challenge to neo-
Darwinism is not a denial that evolution has occurred, let us look at the legitimate scientific
issues that are raised by Gould’s words.
Lamarck Revisited
As we discussed already, most naturalists of the nineteenth century, including Lamarck and
Darwin, concluded that features acquired during one’s lifetime could be passed directly to
descendants (the inheritance of acquired characters). This type of inheritance is unfortu-
nately known as “Lamarckian inheritance”; as we mentioned already, it was an old notion
from before Lamarck and only a minor part of Lamarck’s ideas and was accepted by Darwin
as well. It is obvious why this idea is appealing. Instead of the wasteful Darwinian mecha-
nism of the death of many offspring, just so a few favorable variants can survive, Lamarck-
ian inheritance allows new variations to be passed on directly in a single generation and
allows organisms to adapt more readily.
By the 1880s, however, some geneticists began to doubt whether Lamarckian inheritance
was real. Instead, they asserted the primacy of Darwinian natural selection. The German
biologist August Weismann performed a series of experiments that seemed to discredit the
idea of the inheritance of acquired characters. He cut off the tails of twenty generations of
mice, but each new generation developed a tail, despite this rather extreme form of selec-
tion pressure. From this, Weismann concluded that anything that happens to our bodies
(“soma” in Weismann’s terminology) during our lifetimes does not get back into the genome
(“germ line”). This became known as “Weismann’s barrier” or the central dogma of genetics:
the flow of information is a one-way flow, from genotype to phenotype, but not the reverse.
When James Watson and Francis Crick discovered DNA, the central dogma was redefined
to mean the one-way flow of information from DNA to RNA to proteins to phenotype—but
never back to the DNA.
For decades, the central dogma seemed to work, and even the hint of Lamarckism was
considered highly controversial and unorthodox. But as early as the 1950s, embryologist
Conrad Waddington showed that repeated environmental stresses could cause abrupt genetic
change without direct selection, or what he called genetic assimilation. The best evidence,
however, comes from immunology. When we are born, our immune system is functional
but does not yet recognize all the foreign germs and pathogens it must defend against. We
acquire immunity through our lifetimes each time our immune system is exposed to a germ
and develops an antibody to defend against it. However, a series of experiments showed that