Paper 19

A new evolutionary law.

Van Valen, L. 1973. Evolutionary Theory 1: 1-30.

Blog by Willow

Blurb Author

Matthew A. Kosnik

Phd from U. Chicago

Senior Lecturer at Macquarie U (Australia)

Dr Kosnik's research uses fossil deposits to understand modern marine communities. His research on marine invertebrates has spanned the Phanerozoic, but he is currently concentrating on understanding shell deposits found in Holocene sediment and the impact of western colonisation on Australian marine communities.

Paper Author

Leigh Van Valen

PhD from Columbia U. under George Gaylord Simpson and Theodosius Dobzhansky

Died 2010

http://leighvanvalen.com/

Most of my work has been in paleontology, ecology, genetics, macroevolution, and philosophy, but I’ve done a good deal of work in other areas in and outside of biology. An advantage of being a generalist is the ability to see important gaps in a wide variety of areas. My work has been more in finding new ways to look at gaps rather than filling them in, although I’ve done quite a bit of the latter too. I’ve originated a moderate number of widely used concepts, not all uniquely, probably the most important being:

·      Fluctuating asymmetry

·      Fuzzy sets (as later renamed by Zadeh)

·      Red Queen’s Hypothesis (which has always been primarily a hypothesis in ecology)

·      Metapopulations (published a few months earlier by Levins, but our only communication on it had been from me to him; the term is his)

·      Source-sink equilibria (published a few months earlier by Lidicker, in a book I hadn’t seen; the term is his)

·      Ecological species concept

·      Hennig’s Principle, published before I or most other non-Germans had heard of his earlier book (but this one might be considered reinventing a wheel)

·      There is also something called Van Valen’s Test in statistics, to which the current Encyclopedia of Statistical Sciences devotes four pages.

I founded two journals that partly filled large gaps (by their approaches rather than subject matter). I avoid hot areas, including those I’ve originated myself. In general I try to do work nobody else is likely to do, at least not in ways that I want to do it.

Also wrote “Utterly original, scientifically accurate and occasionally R-rated” biology songs.

Paper

Main Question

         Do survivorship curves show a pattern and, if so, why?

Methods

         Plotted survivorship curves for various families over time to look for patterns and exceptions.

Results

·   Expectthat individuals and subgroups should have concave/convex survivorship. 

o   Their rates of extinction and origination are known to change.

o   Species with small ranges have higher rate of extinction than species with big ranges.

o   Genera that have more species are more likely to have one of those species survive.

·   Observea linear, nearly constant rate of survivorship/extinction rate at family level

Discussion

·   A NEW LAW- extinction in any adaptive zone occurs at a constant rate independent of age

o   “How can it be that extinction occurs randomly with respect to age, but nonrandomly with respect to ecology?”

·   Scale dependent

o   All members of a community are trying to outcompete each other by increasing their fitness, but the mean fitness in an adaptive zone is constant over time. 

o   One species gains an advantage that provokes a counter-response that acts as a detriment to the first species. Fitness of individual species is always changing, but the adaptive zone’s species change together such that the total fitness is always balanced.

o   Environmental perturbations are not independent of each other over time and carry no lasting effects on rates of extinction and therefore are averaged out and inconsequential.

o   An adaptive zone experiences homeostasis on large time scales where, although things may have short changes, all events average out to stay constant.

·   Red Queen Hypothesis

o    

o   To keep ahead of changes, species must be constantly evolving. This doesn’t gain them any long term advantages in their zones, it just momentarily keeps them from going extinct.

o   https://gifrific.com/bird-walking-wrong-way-on-escalator/

§  Bird continues to adapt to its situation, but time progresses and the steps “adapt” in the opposite way

·   Molecular evolution

o   Irregularities in rate of evolution on any scale are evened/averaged out over long periods of time

Conclusion

o   “Each species is part of a zero-sum game against other species….no species can ever win, and new adversaries grinningly replace the losers.” 

o   Small scale examination shows you rapid evolution and various amounts of change in response to environmental changes and coevolution.

o   Big scale examination shows that each of the species are doing the same thing and that all of their evolutionary actions average out to “no progress.”

         

Thoughts 

Kosnik says in his introduction that Van Valen is “exceptional for its breadth of scale.” On one hand, I can see why it was rejected my goodness have someone else read through your manuscripts. But on the other hand, it was very interesting to see how the theory applied and how it changed on different scales. Van Valen made the comment that this law was unlike others because it was not universal. I was initially confused by the statement, but it is fundamental to the theory that on different scales, you see different things, but when you zoom out, nothing truly changes.