Flatlife Has More Genes Than It Needs
The genome of a placozoan (“flat animal”) shows more complexity than one would expect for a simple life form. According to evolutionists, it shows that even a barely-differentiated animal presumably ancestral to complex animals had the genetic toolkit of its more-advanced descendents.
Trichoplax adhaerens is a slimy-looking thing that sticks to aquarium walls. Science Daily has a picture of it. The article says the genome is “confounding [the] array of complex capabilities” because it “appears to harbor a far more complex suite of capabilities than meets the eye.” Although the organism only has 4 or 5 cell types and no organs or gut, its genome “encodes a panoply of signaling genes and transcription factors usually associated with more complex animals.” This includes genes for neurons even though it has no nerves, and hints of genes for sexual reproduction even though it usually divides by fission. It even has a “parts list” for embryo formation but has not been observed to go through an embryo stage.
Another surprise is that T. adhaerens contains 80% of the same introns as humans – in much the same arrangement. Introns have been considered genomic “junk” that must be removed during translation. That these parts are “conserved” (unevolved) from a primitive animal to a human being seems to point to a function for introns and their specific arrangements. Fruit flies and other advanced life, though, have far fewer introns.
The original paper in Nature1 summarized the surprises:
The compact genome shows remarkable complexity, including conserved gene content, gene structure and synteny [i.e., conserved linkage without requiring colinearity] relative to human and other eumetazoan genomes. Despite the absence of any known developmental program and only a modest number of cell types, the Trichoplax genome encodes a rich array of transcription factors and signalling genes that are typically associated with embryogenesis and cell fate specification in eumetazoans, as well as other genes that are consistent with cryptic patterning of cells, unobserved life history stages and/or complex execution of biological processes such as fission and embryonic development in these enigmatic creatures.
One of the authors of the paper said, “Trichoplax has had just as much time to evolve as humans, but because of its morphological simplicity, it is tempting to think of it as a surrogate for an early animal.”
Update 08/23/2008: Elisabeth Pennisi, reporting for Science,2 added rhetoric to the “surprise effect” coming from this genome. Trichoplax “barely qualifies as an animal.” she said. It is one millimeter long and covered with cilia. It glides along like an amoeba. It usually divides by budding or fission. One biologist was quoted saying, “Yet this animal’s genome looks surprisingly like ours.” Here are some other quotes from her news report:
- It’s a puzzle why Trichoplax, a seemingly primitive animal, has such a complex genome.
- Biologists had once assumed that complicated body plans and complex genomes went hand in hand. But T. adhaerens’s genome … “highlights a disconnect between molecular and morphological complexity,” says Mark Martindale, an experimental embryologist at the University of Hawaii, Honolulu. Adds Casey Dunn, an evolutionary biologist at Brown University, “It is now completely clear that genomic complexity was present very early on” in animal evolution.
- Despite being developmentally simple–with no organs or many specialized cells–the placozoan has counterparts of the transcription factors that more complex organisms need to make their many body parts and tissues.
- “Many genes viewed as having particular ‘functions’ in bilaterians or mammals turn out to have much deeper evolutionary history than expected, raising questions about why they evolved,” says Douglas Erwin, an evolutionary biologist at the Smithsonian National Museum of Natural History (NMNH) in Washington, D.C.
1. Srivastava et al, “The Trichoplax genome and the nature of placozoans,” Nature 454, 955-960 (21 August 2008) | doi:10.1038/nature07191.
2. Elizabeth Pennisi, “Genomics: ‘Simple’ Animal’s Genome Proves Unexpectedly Complex,” Science, 22 August 2008: Vol. 321. no. 5892, pp. 1028-1029, DOI: 10.1126/science.321.5892.1028b.
The predictions of evolutionists that they would find Darwin’s tree of life in the genomes of organisms has been falsified. Genomes do not show a straightforward progression from simple to complex, with gradual acquisition of new function over time. The evo-talk in the article and paper sounds forced and superfluous. It may be “tempting” to “think of it” as a primitive evolutionary thing, but moral philosophy admonishes us to overcome temptation.
The genetic toolkit appears established early on. In addition, gene count, chromosome number, and intron content appear indifferent to evolutionary relationships. Trichoplax shows that simple organisms can have complex genes they don’t use – another contradiction with evolutionary expectations. The relationship between genotype and phenotype appears much more elaborate than any evolutionary biologist expected. Whatever is going on, it is time to think outside Darwin’s black box.