Complex structures evolved from simpler structures

“To suppose that the eye,” wrote Darwin, “could have been formed by natural selection, seems, I freely confess, absurd in the highest possible degree.” But Darwin argued that we must not be misled by our intuitions. Given natural selection operating on inheritable variations, some of which are useful, then, if a sequence of numerous small changes from a simple and imperfect eye to one complex and perfect can be shown to exist, and if the eye is somehow useful at each step, then the difficulty is resolved. (Darwin, 143) The key was to identify “a long series of gradations in complexity, each good for its possessor” which could lead to “any conceivable degree of perfection.” (Darwin, 165)
 
But ever since Darwin the list of complex structures in biology, for which no “series of gradations in complexity” can be found, has continued to grow longer. Both the fossil record and genomic data reveal high complexity in lineages where evolution expected simplicity. As one evolutionist explained:
 
It is commonly believed that complex organisms arose from simple ones. Yet analyses of genomes and of their transcribed genes in various organisms reveal that, as far as protein-coding genes are concerned, the repertoire of a sea anemone—a rather simple, evolutionarily basal animal—is almost as complex as that of a human. (Technau)
 
Early complexity is also evident in the cell’s biochemistry. For instance, kinases are a type of enzyme that regulate various cellular functions by transferring a phosphate group to a target molecule. Kinases are widespread across eukaryote species and so they must persist far down the evolutionary tree. And the similarity across species of the kinase functions, and their substrate molecules, means that these kinase substrates must have remained largely unchanged for billions of years. The complex regulatory actions of the kinase enzymes must have been present early in the history of life. (Diks)
 
This is by no means an isolated example. Histones are a class of eukaryote proteins that help organize and pack DNA and the gene that codes for histone IV is highly conserved across species. So again, the first histone IV must have been very similar to the versions we see today. An example of early complexity in eyes is found in the long-extinct trilobite. It had eyes that were perhaps the most complex ever produced by nature. One expert called them “an all-time feat of function optimization.” (Levi-Setti, 29) Reviewing the fossil and molecular data, one evolutionist explained that there is no sequential appearance of the major animal groups “from simpler to more complex phyla, as would be predicted by the classical evolutionary model.” (Sherman) And as one team of evolutionists concluded, “comparative genomics has confirmed a lesson from paleontology: Evolution does not proceed monotonically from the simpler to the more complex.” (Kurland)
 
References
 
Darwin, Charles. 1872. The Origin of Species. 6th ed. London: John Murray.
http://darwin-online.org.uk/content/frameset?itemID=F391&viewtype=text&pageseq=1
 
Diks, S., K. Parikh, M. van der Sijde, J. Joore, T. Ritsema, et. al. 2007. “Evidence for a minimal eukaryotic phosphoproteome?.” PLoS ONE 2.
 
Kurland, C., L. Collins, D. Penny. 2006. “Genomics and the irreducible nature of eukaryote cells.” Science 312:1011-1014.
 
Levi-Setti, Riccardo. 1993. Trilobites. 2d ed. Chicago: University of Chicago Press.
 
Sherman, M. 2007. “Universal genome in the origin of metazoa: Thoughts about evolution.” Cell Cycle 6:1873-1877.

Technau, U. 2008. “Evolutionary biology: Small regulatory RNAs pitch in.” Nature 455:1184-1185.