There are a lot of things that biological systems do that we don’t understand yet. Most intriguing are the things that seem to have no basis in physics or chemistry as we understand them. These phenomena don’t tend to attract researchers because they’re hard to study and there’s no funding available for exploratory research that necessarily has a high failure rate. Nevertheless, this is where the most interesting science is.
- When a stem cell population is depleted, ordinary (epithelial) cells can turn themselves “back” in the development process, into stem cells again to fill the niche.
- When the body is injured, protective cells and rebuilding cells in distant parts of the body somehow get the word, and begin an odyssey into the area that needs them most. [journal article]
- Terns migrate up to 57,000 miles a year (twice around the earth). Sea turtles return to their breeding ground from thousands of miles away. We have no idea how they navigate.
[I]n the ecological view the context or history of environments determines the meaning of any stimulus or information we encounter. We sense that explanation in the example above in which an epithelial cell stands in for a stem cell (or coopts that niche). No cell in the vicinity of that niche is needed to signal specifically that the stem cell is missing (how would it know?). So, as in the wound-recovery example, the notion that some specific command signal directed to it causes the epithelial cell to immigrate is unconvincing.