PANDAS

The odd things in nature illustrate best how natural selection works. Charles Darwin used orchids extensively. Stephen Jay Gould uses the Panda to help us understand the workings of nature. It is not the perfect form that should amaze us. It should be the imperfect and odd. A Giant Panda is familiar to all of us. These are peculiar bears. Our picture of a bear is one that scratches and claws and eats meat. The conventional bear is omnivorous. Yet Pandas eat almost exclusively bamboo. In fact, they tend to eat bamboo for 8 to 12 hours every single day. They tend to sleep nearly as much. They don't even seem to process this food very well as they tend to deficate nearly 90% out the other end. They conserve energy even as they eat! Talk about laid back - Pandas are just that.

Yet Giant Pandas eat bamboo relatively well despite the fact that they are bears. They possess a relatively dexterous hand with an opposable thumb. This hand enables them to grab bamboo and pull off leaves to eat. This hand would win no prise for design. In contrast to ours it is very clumbsy. It is not constructed like our hand either. There are five Panda fingers and a thumb. The thumb is actually a part of the wrist known as the radial sesamoid. The thumb is a jury-rigged bone (the radial sesamoid bone), cartledge, and muscle. Count the claws in the picture below and then notice the "nob" that you can see the Panda holding the bamboo stalk with.

You may be wondering how a bear gets a "thumb" at all. The answer lies in the fact that bears as a group tend to have an enlarged radial sesamoid bone and a more flexible "paw". The Giant Panda had this available and Pandas with larger radial sesamoids and greater flexibility succeeded in eating more bamboo. These individuals had more energy. They lived longer and tended to be better fit to reproduce.

Giant Pandas are not good at what they do. They were designed to do what other bears normally do. Their hand is not well designed but it works effectively based on what was available. Their ability to develop the thumb and dexterous hand were contingent on the fact that bears have a relatively flexible "paw". Pandas tend to eat and sleep most of every day. They don't process their food well. Their reproductive success as a whole is not good. Yet, they survive. Giant Pandas are examples of how nature jury-rigs from available components and does not necessarily do a "well designed" job either. Through natural selection, individuals with the best components - maybe only marginally "best" - succeed more often in reproducing and passing on their "better" ability.

One last piece of trivia about Pandas. They tend to live solidary lives. They don't seem to like each other very much in other words. They mark their territory with scent to notify other Pandas they "own" an area. Females have a very limited reproductive cycle that lasts only for one to three days each year. Males have to be very cautious as they approach a female not to be attacked given how they normally don't like each other. During the reproductive period in the year, not only do males have to approach a female with a bit of finess but they also may have to do battle with other males who would like to reproduce....all of this takes energy which is at a premium for Giant Pandas. In other words, life does not seem to be very easy at any time...perhaps except when they sleep which is quite a bit!