A perfect fossil record  Yesterday, November 24, was the anniversary of the publication of Char

A perfect fossil record Yesterday, November 24, was the anniversary of the publication of Charles Darwin’s book “Origin of Species” which described how life evolves over time. The story of Earth is very much the story of life. Life has profoundly shaped our planet, from completely changing the atmosphere to impacting the distribution of elements and isotopes in the mantle. From a geological perspective, one of the most fascinating products of evolution is the fossil record. Rocks worldwide provide records of evolution going back billions of years. The appearance of certain chemicals can mark the evolution of certain traits by life and life has found ways to create many of the rocks and minerals found at the surface of Earth today. The fossil record is in many ways spectacular. It’s a multi-billion year record of the evolutionary experiment. But, in other ways, it does have its weaknesses. We can’t, for example, find evolution of every single species; some of them just aren’t preserved, particularly ones without hard parts or single-celled creatures. We also have to accept some margin of error on the measurements. We can come up with remarkably precise age estimates, knowing how old some biologic process or fossil is to within a million years even billions of years ago, but it’s really tough to do better than “within a million years” and when things change rapidly, that’s still a large margin of error. You’re looking at one way to do science while working around that problem. 25 years ago, Dr. Richard Lenski (now at Michigan State University) put a sample of the bacteria E coli into a series of 12 flasks with some sugar and allowed them to do what they wanted. Each day, a small portion of each sample of bacteria was transferred to a new flask and every 75 days a portion was frozen to allow for record keeping.The results today are a spectacular scientific record. Because E Coli goes through several generations per day, the samples have passed through 58,500 generations; in human lifetime this is the equivalent of over a million years of evolution. The different flasks produced different properties as a result of random mutations. The ability to process certain compounds like citrate evolved independently several times in different ways (here you see the grad student who worked on what it took for the ability to process that compound sitting in front of the samples he worked on, effectively sitting in front of a fossil record). One flask evolved 2 independent populations that had different habits – one made large colonies, one made small colonies, and they have existed together ever since. Effectively this experiment is a perfect fossil record. The processes we can’t always find in the real fossil record, the evolution of specific traits, the birth of new species and the extinction of others, are recorded in those freezers with exceptional detail. Just like life on the actual Earth, evolution in those vials continues to this day; the evolutionary arms race never slows down. -JBB Image credit: Science Magazine (reproduced for education and outreach):http://www.sciencemag.org/content/342/6160/790.full  -- source link

More pics about