Science Literature

What can be said about the origin of the eukaryotic cell? "Until recently, everyone assumed, based on a single ribosomal RNA gene, that eukaryotes descended from archaebacteria - extremophilic prokaryotes distinct from 'true' bacteria, or eubacteria. Now we know that's not the case.' Genome studies reveal links with eubacteria as well as archaebacteria. There are also numerous losses of genes that are puzzling: "But how did evolution come up with the strange distribution of eubacterial and archaebacterial genes we see in eukaryotes today?"
In passing, we must note that an explanation in terms of evolutionary theory is assumed as a 'given'. It is as though no other avenues need be explored.
A remarkable paradox is introduced thus: "Because eukaryotes are derived from archaebacteria and eubacteria, one might expect to find an archaebacterial and a eubacterial copy of each nuclear gene. But strangely, archaebacterial operational and eubacterial informational genes are almost completely absent from eukaryotes, even though the first eukaryote contained two sets of informational and operational genes."
The author, James Lake, uses the analogy of the Roman god Janus. "Like the two faces of the Roman god Janus, thought to represent the Moon and the Sun, the phylogenetic origins of informational and operational genes in eukaryotes are as different as night and day. Finding a gene distribution such as this is the statistical equivalent of finding that a coin tossed at night (Janus's archaebacterial face) always comes up heads (informational genes), and tossed during the day (Janus's eubacterial face) always comes up tails (operational genes)."
Lake then discusses possible explanations of the Janus paradox. He offers a possible explanation as to why the eubacterial informational genes disappeared, but that's as far as he goes. "Unfortunately, I have no good suggestion for why the archaebacterial operational genes were eliminated." He concludes: "How the eukaryotic cell came to be is one of the greatest enigmas in biology. It is a story so complex that no single gene can tell it. Only entire genomes can."
The more we look at eukaryotes, the more obvious it becomes that an evolutionary story of simple to complex is woefully inadequate. But will genome studies help? Last year, the authors of a research paper wrote: "we review recent data from proteomics and genome sequences suggesting that eukaryotes are a unique primordial lineage". Some paradoxes can only be solved by changing the paradigm: maybe the avenue to be explored is signposted "intelligent design".

Disappearing act
James A. Lake
Nature 446, 983, (26 April 2007) | doi:10.1038/446983a
The bizarre absence of certain gene classes in eukaryotes is key to understanding their evolution and complex links with prokaryotes.

See also:
Kurland, C.G., Collins, L.J. and Penny, D. Genomics and the Irreducible Nature of Eukaryote Cells, Science 312, 19 May 2006: 1011-1014.

Wing morphology has a profound effect on aerodynamic performance. Gliding birds such as swifts exploit their ability to morph their wings: "Extended wings are superior for slow glides and turns; swept wings are superior for fast glides and turns. This superiority is due to better aerodynamic performance - with the exception of fast turns. Swept wings are less effective at generating lift while turning at high speeds, but can bear the extreme loads."
New research has led to a more refined aerodynamicmodel, enhancing understanding and stimulating ideas for future developments in aircraft design. "Lentink says that these aircraft designs are crude compared with what the swifts can do, thanks to the engineering challenges involved. "The swifts are just better at it," he says, "The amount of feathers and muscle involved is challenging for us [to imitate].""
One might anticipate that research like this might stimulate thoughts about intelligent design. That is certainly the way engineers have to approach their work. The glide speeds at which the birds minimize energy expenditure have been determined. But one of the co-authors is quoted as saying: "They [swifts] have evolved an aerodynamic design for cheap flight". However, there is nothing in this research that suggests that these capabilities are evolved rather than intelligently designed. This comment linking design to an evolutionary origin is theory-laden and is actually a pointer to a socially-constructed 'reality' adopted by the researcher.

How swifts control their glide performance with morphing wings
D. Lentink, U. K. Muller, E. J. Stamhuis, R. de Kat, W. van Gestel, L. L. M. Veldhuis, P. Henningsson, A. Hedenstrom, J. J. Videler and J. L. van Leeuwen.
Nature 446, 1082-1085 (26 April 2007) | doi:10.1038/nature05733

Gliding birds continually change the shape and size of their wings1, 2, 3, 4, 5, 6, presumably to exploit the profound effect of wing morphology on aerodynamic performance7, 8, 9. That birds should adjust wing sweep to suit glide speed has been predicted qualitatively by analytical glide models2, 10, which extrapolated the wing's performance envelope from aerodynamic theory. Here we describe the aerodynamic and structural performance of actual swift wings, as measured in a wind tunnel, and on this basis build a semi-empirical glide model. By measuring inside and outside swifts' behavioural envelope, we show that choosing the most suitable sweep can halve sink speed or triple turning rate. Extended wings are superior for slow glides and turns; swept wings are superior for fast glides and turns. This superiority is due to better aerodynamic performance - with the exception of fast turns. Swept wings are less effective at generating lift while turning at high speeds, but can bear the extreme loads. Finally, our glide model predicts that cost-effective gliding occurs at speeds of 8-10 m s-1, whereas agility-related figures of merit peak at 15-25 m s-1. In fact, swifts spend the night ('roost') in flight at 8-10 m s-1 (ref. 11), thus our model can explain this choice for a resting behaviour11, 12. Morphing not only adjusts birds' wing performance to the task at hand, but could also control the flight of future aircraft7.

See also:
Ledford, H. Wings in a wind tunnel show secrets of flight. Study of swifts could improve airplane designs.
news@nature.com, 25 April 2007 | doi:10.1038/news070423-7