Neil Shubin continued his Hitchcock Lecture here at UC Berkeley, California. Yesterday’s lecture was about how our ancient ancestors managed to get out of the water and walk on dry land and today’s was more about the similarities of bones of many different species through time and their niche space.
The slide above shows a consistent pattern of one large bone coming from the shoulder, articulating with two bones at an elbow, then from those a group of small bones, and then from them some longer bones. This pattern existed since very ancient times and developed through adaptation to very many different uses. He spoke of this with the metaphor of a tool box of basic possibilities being exploited in different ways.
All of my friends from the Med asked questions at the end of the lecture which I thought Shubin fielded quite well although Len needed some explanation and convincing from me and Brian on our 15 minute walk towards our respective destinations. My question, which I never succeeded in articulating very well, because I really was exploring outside of his official field, it was sort of a meta question.
There was a basic tool-box of existing bones long ago, long before his special creature the Tiktaalik roseae came out of the water some 375 million years ago. That was at the heart of today’s lecture. The physical manifestations of this toolbox, packaged genes of information, were made manifest in the bones pictured above. Each of these bones formed as buds of cells early in their embryonic development and continued with very similar types of function within their part of the living animal even though that function might be very different to the outside world where that assemblage of bones found their application. For example the first bone, the single one attached to the shoulder was always a swinging around in a revolving type of motion, the pair of bones was a rotating twisting motion where needed, the wrist assemblage an articulating left-right up-down attachment for the final longer bones which were directly used for acting on the animals environment. To me it seemed the toolbox was a useful metaphor but it was always interacting with and was thus mediated by many other things such as the environmental use to which it was being put. Perhaps, these other things could be considered toolboxes also.
It seems we have a minimum of three factors to be contended with, each of which can be toolboxes, themselves sub-dividable: 1. The genes and chromosomes and their physical limitations and possibilities, 2. The mechanical properties and limitations of the various bone and cartilage materials from which the animal’s bony structure is constructed and 3. The external environmental constraints, and forcings which determine what the animal can and can not do.
All of this complicated structured and process must be coupled with the absolute necessity that the creature must survive and reproduce in an always challenging and frequently changing environment. I think my question broke down because there were just to many different interacting factors to make the question comprehensible let alone answerable.
Len, Brian, Jean and Richard all got interesting answers to their questions. One of the qualities which develops from time spent in the Med is the willingness to step up and challenge, usually respectufully, the authorities with good questions.