February 2003
Dog Evolution Studied
A recent Chicago Tribune article reported on studies on dogs and their evolution. It appears that dogs were first bred in China about 15,000 years ago. Testing has been done on ancient dogs dug out of the permafrost along with behavioral tests on modern dogs. When you look at the fact that humans have bred dogs into the most widely diverse species of mammals on the planet in a very short period of time compared to natural evolution. With DNA from hundreds of dogs worldwide, it looks like there were just a few original groups of wolves in East Asia that gave rise to all of today’s dogs. In another study (at Harvard) dogs are found to do better than chimps in some simple cognitive tests. Chimps are the ones most often thought to be most similar to humans. In a third study DNA was taken from North American fossil dogs including 11 from the permafrost in Alaska. There were also some from Mexico and Peru. They are all dated to before European explorers arrived. This DNA showed that the early arrivals brought their dogs from Asia rather than domesticating wolves found in the new country. They may have helped in the survival of humans by providing some security and help with hunting. They are interesting because with changes in relative few gene sites they have been bred to handle a wide variety of skills with training. Think of the specialists known today - herding dogs, sledding dogs, hunters, etc. One of the simple tests run was taking human signals to find food. The researcher might give a subtle pointing clue and in all cases the dogs did much better than chimps or wolves. The fact that dogs can understand subtle human cues means that they must be thinking about the thoughts of others. Now that the human genome is known maybe they will work on the dog genome soon. There may be more we can learn about evolution from these animals than was thought before.
Evidence of Dinosaurs After K/T
In an article in a Special Paper from the Geological Society of America, Fassett et al report on evidence for Paleocene dinosaurs in New Mexico. They carefully dated the site to be sure that it was not reworked and date the fossils at 64.5 MYA or one million years after the K/T boundary when dinos were believed to have gone extinct (65.5 MYA). They found 34 bones from a single hadrosaur. They can not name the species as cranial material is necessary to determine that. They found other bones also and have named the assemblage the Alamoan Fauna for the Ojo Alamo Sandstone (named by Barnum Brown in 1920) where it is found. It was dated as Cretaceous when first named because there were dinosaur bones in it. In 1924 a researcher said it was Tertiary based on some plant fossils found. More recent plant material analysis agrees with the Paleocene dating. The geochemical composition of the bones differ from the underlying dino bones found from the Cretaceous Kirtland Formation. Other dino bones found have been identified as ornithomimid, dromaeosaurid, sauronithoidid, Albertosaurus, Tyrannosaurus, Alamosaurus, ankylosaurid, nodosaurid, Torosaurus, Pentaceratops, and hadrosaurids. The extinction of these survivors is dated to 64.5 MYA. They suggest that one explanation could be that there were a large number of buried dinosaur eggs just before the asteroid impact that then survived for the first year or two after the impact.
Extinction of Trilobites
What happened to the trilobites at the end of the Permian? The trilobites were very numerous and ranged from animals less than an inch in length to animals over a foot long. The main theory to date is predation because of the increase in the number of predators at this time. However this is unlikely to occur. Other arthropods survived the same predators. Other theories include climate change, sea level fluctuation, and a meteorite - all familiar explanations. Now research from Michigan State University puts forth a new possible explanation. It seems that most animals that molt, molt the same way every time and many of them eat their molts to get the nutrients needed for a new outer shell. Apparently trilobites got rid of their old shells any way they could. Because this is a very vulnerable time for them, many things could go wrong. The evidence is the inconsistency of molting patterns in trilobites and the fact that the trilobites with fewer body segments tended to live longer. The lesser segmented animals could probably shed more easily with fewer complications. They also have found no evidence that trilobites consumed their shed exoskeletons. They would have to rebuild their exoskeleton from scratch each time. I’ll be interested in seeing what other invertebrate people think of this theory.
Galapagos Finches Under Attack
The famous finches that played an important part in Darwin’s development of evolution theories are now fighting off an invader. It seems that some flies arrived in shipments of fruit or vegetables and are thriving on the islands. The larvae of the flies live in the finch nests and burrow into the nestlings sucking their blood. A study of the birds from 1997 to 2000 showed that a quarter of the nestlings infected by the flies died. They could fumigate the nests to get rid of the flies, but some feel that the best hope is for the finches to learn to live with the pests.
New Chinese Ankylosaur Named Crichtonsaurus
Well, it looks official that Michael Crichton does have a dinosaur named after him. Dong Zhi-Ming reports in Vertebrata Palasiatica on a new genus and species named Crichtonsaurus bohlini (Bohlin is a Swedish scientist). It comes from the Late Cretaceous Liaoning and the specimen consists of a partial left mandible with 3 teeth, several vertebrae, scapula, corocoid, humerus, femur, and several plates and scutes of dermal armor. Based on the verts, it is estimated to be medium sized at about 9 feet. Finally Michael gets a dino.
More Unknowns Underground?
We often think that the next unknown frontier that contains the most unknown animal species is the vast oceans. However, some think that it is beneath our feet. There is a new 5-year project to study the fauna in 7 world tropical countries. Some estimate there may be as many as 40,000 types of bacteria in a gram of forest soil! That is 10 times the number of bacteria known now. We may have catalogued only 5% of fungi and mites, 15% of nematodes and 50% of earthworms.
Karen Nordquist, ESCONI Paleontology Study Group
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