Evolution Traced to Sponges?

For someone who had "no driving career ambitions" and "never expected to become a scientist", Mitchell Sogin has made some pretty impressive discoveries about evolution. He set out to answer the timeless question, "Where did we come from?" For years he tried to find answers to this question by studying lineal molecular evolution. What he found was completely new to the world of Science.

Sogin has always been interested in evolution. An evolutionary microbiologist, he has been tracing the molecular evolution of some very old species since he opened his lab in 1989. When trying to determine the ancestry of species such as jellyfish, sea anemones, mollusks and starfish, he found something surprising. It appeared that he could trace the ancestry of many animals to sponges! This came as a surprise even to Sogin.

Most people think of sponges as plants. For years, scientists have even published articles about sponges in plant journals. However, according to Sogin, sponges are really animals. This might sound strange, because although sponges are multicellular, these cells do not add up to much. Sponges have no tissue, muscles, organs, nerves or brain. So how could animals have evolved from sponges? According to Sogin's research, it makes plenty of sense. Although sponges have just a few kinds of cells that are connected loosely, they can produce many different asymmetrical shapes. They are also the earliest sexual reproducers.

Prior to Sogin's research, the relationship between different types of animals was mostly determined by the characteristics they shared. The more characteristics that they shared, the more closely related two organisms were assumed to be. Sogin decided to try a different route. Years earlier, Sogin's mentor, Carl Woese, had used a DNA sequence called ribosomal RNA to make some huge discoveries. This sequence proved to be useful for Slogin as well. For years Slogin labored over the endless task of comparing the DNA of many different organisms. He found that sponges and animals share a common evolutionary history from fungi. "I'd say we share a common, unique evolutionary history with fungi. There was a single ancestral group of organisms and some split off the become fungi and some split off to become animals", Sogin explains. According to Sogin, sponges have a lot of organization for their simplicity and all other animals came from this simple architecture.

Sogin's research is definitely interesting to read about, but what other importance might it have? There is a lot of reason to believe that his studies could lead to some huge advances in medicine and treatment of different diseases, such as AIDS. Also, according to Sogin, "Learning how organisms evolved might hold the key to knowing what might happen to us in the future", and this is something everyone is interested in. His studies also have generated some suspicions about extraterrestrial life. Sogin is convinced that any life forms found in outer space will closely resemble sponges.

Source: McClintock J. 2004. This is Your Ancestor. Discover v25, n11. 64-69.