Dive Dry with Dr. Bill

#239: Descended from Urchins?

I try to respect the beliefs of others, especially when it comes to religion and politics. Given some of the trends today in both areas, it is often a difficult task to just keep my mouth shut. For nearly 150 years some people have decried the concept of evolution, and our possible descent from an early primate ancestor that also gave rise to chimpanzees. Given the incredible technology of gene sequencing and the decoding of a species genome, it is very hard to argue with the fact that about 98% of our genes are shared with chimpanzees. Just for clarification, the genome is the complete set of DNA of a species.

What might be even less palatable to the disbelievers is the newly discovered genome of the "lowly" spiny skinned echinoderm known as the purple sea urchin which is reasonably common in our waters. Professor Kathy Folz at UCSB led an international group of scientists that recently decoded the complete genetic structure of Strongylocentrotus purpuratus, which is the name we "egghead" scientists apply to this species. The echinoderms are not vertebrates and have no spinal cord. However, they are among the closest invertebrate relatives to animals with backbones like fish, birds and humans. Don't worry, they are still a "distant" relation to us, but certainly part of our "extended family" (if you allow a slight stretch of the imagination).

Gene sequencing, identifying the genetic structure of a species, provides some of the most irrefutable evidence of the fact of evolution. It is far superior to the guesses scientists in Darwin's time had to apply to the differentiation of species based on physical appearance or behavior. If two species have very similar DNA, it is hard to deny they are closely related evolutionarily.

Now the molecular biology of genes is not something I focused on in college. Heck, it was still a very new science when I attended Harvard, although some of the best scientific minds in that field were there. At the time, those of us focused on ecological studies were actually involved in "wars" (non-lethal) over which disciplines would get coveted laboratory space. As I remember it, one of my favorite professors, Dr. E. O. Wilson, was in one camp and the likes of Dr. J. D. Watson (who co-discovered the structure of DNA) was in the other.

Although I recognized the value of the molecular biologist's contribution to our understanding of biology, my personal interests were in the area of ecology and animal behavior. I much preferred spending time in the field rather than in a lab with lots of glassware and white labcoats. Were I attending college today, the high percentage of beautiful Asian women involved in such research might result in a different choice! However, I still prefer being out in the field, underwater, to being cooped up in a lab all day... and all of the night!

Back to Dr. Folz and her colleagues work. They discovered that the purple sea urchin has 23,000 different genes. For comparison, I was astounded to discover that the human genome is believed to consist of just 30,000 genes, an unexpectedly small number for a species as complex as we think we are! Dr. Folz's team found that over 70% of the purple sea urchin's genes are also found in humans. While that is not close to the 98% in chimpanzees, I thought it was an impressive similarity.

For my friends that still question the "theory" of evolution, please understand that I see no contradiction between a Creator and the mechanism of evolution. Biblical accounts were certainly modified to fit with the understanding of the day, and billions of years were outside the ken of early Christians. However, based on knowledge from a wide range of disciplines, we now can be pretty certain (I'd say 100%) that the Universe is much older than the 6,011 years estimated by Bishop Usher in the 1600's based on a reading of Biblical births and deaths.

Why is the genome of the purple sea urchin important to us? Based on the team's findings, it has a surprisingly complex set of genes that code for the urchin's immune system proteins. It also possesses a complex of gene-controlled proteins that help the urchin deal with environmental stressors. Since echinoderms have calcium carbonate exoskeletons, the genes regulating calcium levels in this species could be important in understanding how the skeletal system of vertebrates like ourselves is maintained. Such knowledge of a "lowly" urchin's genetic system is not just pure science... it has potential medical ramifications for other species, including its 70% "relative," human beings (or Homo sapiens if you prefer). I'm a little concerned if those beautiful Asian molecular geneticists start sequencing my genome... they might discover I'm actually closely related to the little green men (and women) of the planet Xanadu. If that should happen, men in those other white jackets might come and take me away!

© 2007 Dr. Bill Bushing. Watch the "Dive Dry with Dr. Bill" underwater videos on Catalina Cable TV channel 49, 10:00 AM and 5:00 PM weekdays. Please help me climb out of self-imposed poverty... buy my "Munching and Mating in the Macrocystis," "Great White Sharks of Guadalupe," "Calimari Concupiscence: Mating Squid, " "Playful Pinnipeds: California Sea Lions," "Belize It or Not: Western Caribbean Invertebrates, Fish and Turtles," "Gentle Giants: Giant Sea Bass" or "Common Fish and Invertebrates of the Sea of Cortez" DVD's. Yes, take Dr. Bill home with you... we'll both be glad you did!

Your "relative" and mine, the purple sea urchin (notice the "family" resemblance?).

This document maintained by Dr. Bill Bushing.
Material and images © 2007 Star Thrower Educational Multimedia