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Hox hype

Has macro-evolution been proven?

Associate Professor of Biology, and Associate Director, Creation Studies at Liberty University

From the hype of the press release, it would seem that evolution was finally proven once and for all and the creationists should just give up and go home. But far from refuting creation, the scientific evidence is completely consistent with creation!

The press release from UCSD said in part:

‘Biologists at the University of California, San Diego have uncovered the first genetic evidence that explains how large-scale alterations to body plans were accomplished during the early evolution of animals…. The achievement is a landmark in evolutionary biology, not only because it shows how new animal body plans could arise from a simple genetic mutation, but because it effectively answers a major criticism creationists had long leveled against evolution—the absence of a genetic mechanism that could permit animals to introduce radical new body designs.’

Evolutionary biologists believe that the six-legged insect body plan evolved from crustacean-like ancestors (including creatures like shrimp) that lost the large number of legs.1 Such a radical change would require mutation(s) that result in the suppression of leg development. McGinnis and coworkers believed that they found the mutation and the gene responsible for this change. However, careful examination of their efforts reveals that the situation is much more complicated.

The scientists were investigating Ubx, a Hox gene which suppresses leg development in flies. Hox genes are master control switches that control the body plan. Specific Hox genes may control where the head forms, where limbs form, or a tail or even wings. These master switches work like circuit breakers and either turn on or turn off an array of other genes. Hox genes can be expressed in abnormal locations and either prevent development of structures or promote their development in very unusual places. For example Pax-6 expression controls the development of eyes. A fly with abnormal expression could form an eye on a leg, the antenna or even abdomen.2

The researchers found that the Ubx gene from a fly completely prevented leg development while the same gene from Artemia, a brine shrimp, only suppressed leg development 15%. They then mutated the Artemia Ubx gene and found that this version was much more effective at blocking leg formation. They postulated that such a mutation probably occurred in the crustaceans that were the ancestors of six-legged insects.3

The fact that scientists can significantly alter the body plan does not prove macro-evolution nor does it refute creation. Successful macro-evolution requires the addition of NEW information and NEW genes that produce NEW proteins that are found in NEW organs and systems.

For example, a single mutation that might prevent legs from forming is much different from a mutation that produces legs in the first place. Making a leg would require a large number of different genes present simultaneously. Moreover, where do the wings come from? Just because an organism loses a few legs doesn’t convert a shrimp-like creature into a fly. Since crustaceans don’t have wings, where does the information come from to make wings in flies?

Having the wings themselves is not even enough. Researchers in another study have found that the subcellular location of metabolic enzymes is important for the functional muscle contraction required for flight.4 Indeed, the metabolic enzymes must be in very close proximity with the cytoskeletal proteins that are involved in muscle contraction. If the enzymes are not in the exact location in which they are needed within the cell, the flies cannot fly. This study bears out the fact that ‘the presence of active enzymes in the cell is not sufficient for muscle function; colocalization of the enzymes is required.’ It also ‘…requires a highly organized cellular system.’

Therefore, changes in body plan—no matter how dramatic—do not automatically prove macro-evolution. Losing structures, or misplacing their development, should not be equated with the increased information that is needed to form novel structures and cellular systems.

Published: 15 February 2002

References and notes

  1. Ronshaugen, M, McGinnis, N, and McGinnis, W. Nature advance online publication, 6 February 2002 (DOI 10.1038/nature716). Return to text.
  2. Halder, G, Callaerts, P, Gehring WJ. Science 267:1788–92 1995. Return to text.
  3. Ref. 1. Return to text.
  4. Wojtas K, Slepecky N, von Kalm L, Sullivan D. Mol Biol Cell 8:1665–75 1997. Return to text.