Critics of evolution cite scientific debates to undercut Darwin's credibility. That strategy fails when research clears up some of the issues. Results from two separate research projects announced this week make that point.
They deal with Darwin's controversial suggestion that new species can arise within an ancestral population even when there is no way to separate the diverging groups geographically.
There's plenty of evidence that new species arise when segments of a single population become geographically separated, as Darwin also theorized. His other suggestion has lacked such evidence. It has remained what Axel Meyer and his colleagues at the University of Konstanz in Germany call "one of the most controversial concepts in evolutionary biology."
They present in the journal Nature what they consider "a convincing case" that Darwin was right.
They found their proof in Nicaragua's isolated volcanic crater Lake Apoyo. There, two species of cichlid fish - Midas cichlid and Arrow cichlid - live together. Detailed genetic, morphological, and ecological study confirms their relationship as separate species that evolved from a common ancestor. They live separate lives in the same geographical space. Misas feeds along the bottom. Arrow exploits the open water. The two do not interbreed.
The researchers explain why they are convinced that the two species did not evolve elsewhere and then invade the lake after it formed about 23,000 years ago. Once the ancestral population was established, however, evolution progressed rapidly.
The team estimates that the new species appeared in less than 10,000 years - a blink of the eye in geological time.