SSBG

A worldview is a set of claims that purport to be based on ultimate reality.

The Scientific Controversy Over Whether Microevolution Can Account For Macroevolution

Posted by ssbg on August 28, 2006

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From: http://www.dissentfromdarwin.org/

© Center for Science and Culture/Discovery Institute, 1511 Third Avenue, Suite 808, Seattle, WA 98101

When Charles Darwin published The Origin of Species in 1859, it was already

known that existing species can change over time. This is the basis of artificial breeding,

which had been practiced for thousands of years. Darwin and his contemporaries were

also familiar enough with the fossil record to know that major changes in living things

had occurred over geological time. Darwin’s theory was that a process analogous to

artificial breeding also occurs in nature; he called that process natural selection. Darwin’s

theory was also that changes in existing species due primarily to natural selection could,

if given enough time, produce the major changes we see in the fossil record.

After Darwin, the first phenomenon (changes within an existing species or gene

pool) was named “microevolution.” There is abundant evidence that changes can occur

within existing species, both domestic and wild, so microevolution is uncontroversial.

The second phenomenon (large-scale changes over geological time) was named

“macroevolution,” and Darwin’s theory that the processes of the former can account for

the latter was controversial right from the start. Many biologists during and after

Darwin’s lifetime have questioned whether the natural counterpart of domestic breeding

could do what domestic breeding has never done — namely, produce new species, organs,

and body plans. In the first few decades of the twentieth century, skepticism over this

aspect of evolution was so strong that Darwin’s theory went into eclipse. (See Chapter 9

of Peter Bowler’s Evolution: The History of an Idea, University of California Press,

revised edition, 1989).

In the 1930s, “neo-Darwinists” proposed that genetic mutations (of which Darwin

was unaware) could solve the problem. Although the vast majority of mutations are

harmful (and thus cannot be favored by natural selection), in rare instances one may

benefit an organism. For example, genetic mutations account for some cases of antibiotic

resistance in bacteria; if an organism is in the presence of the antibiotic, such a mutation

is beneficial. All known beneficial mutations, however, affect only an organism’s

biochemistry; Darwinian evolution requires large-scale changes in morphology, or

anatomy. Midway through the twentieth century, some Darwinian geneticists suggested

that occasional “macromutations” might produce the large-scale morphological changes

needed by Darwin’s theory. Unfortunately, all known morphological mutations are

harmful, and the larger their effects the more harmful they are. Scientific critics of

macromutations took to calling this the “hopeful monster” hypothesis. (See Chapter 12

of Bowler’s book.)

The scientific controversy over whether processes observable within existing

species and gene pools (microevolution) can account for large-scale changes over

geological time (macroevolution) continues to this day. Here are a few examples of peerreviewed

scientific articles that have referred to it just in the last few years:

David L. Stern, “Perspective: Evolutionary Developmental Biology and the

Problem of Variation,” Evolution 54 (2000): 1079-1091.

“One of the oldest problems in evolutionary biology remains largely unsolved…

Historically, the neo-Darwinian synthesizers stressed the predominance of

micromutations in evolution, whereas others noted the similarities between some

dramatic mutations and evolutionary transitions to argue for macromutationism.”

Robert L. Carroll, “Towards a new evolutionary synthesis,” Trends in Ecology

and Evolution, 15 (January, 2000): 27.

“Large-scale evolutionary phenomena cannot be understood solely on the basis of

extrapolation from processes observed at the level of modern populations and

species.”

Andrew M. Simons, “The continuity of microevolution and macroevolution,”

Journal of Evolutionary Biology 15 (2002): 688-701.

“A persistent debate in evolutionary biology is one over the continuity of

microevolution and macroevolution — whether macroevolutionary trends are

governed by the principles of microevolution.”

It should be noted that all of the scientists quoted above are believers in Darwinian

evolution, and that all of them think the controversy will eventually be resolved within

the framework of that theory. Stern, for example, believes that new developmental

studies of gene function will provide “the current missing link.” (p. 1079) The important

point here is that the controversy has not yet been resolved, precisely because the

evidence needed to resolve it is still lacking. It is important for students to know what the

evidence does or does not show — not just what some scientists hope the evidence will

eventually show.

Since the controversy over microevolution and macroevolution is at the heart of Darwin’s

theory, and since evolutionary theory is so influential in modern biology, it is a disservice

to students for biology curricula to ignore the controversy entirely. Furthermore, since

the scientific evidence needed to settle the controversy is still lacking, it is inaccurate to

give students the impression that the controversy has been resolved and that all scientists

have reached a consensus on the issue.

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