Making new evolutionary innovations efficiently (Introduction)

by David Turell @, Monday, January 20, 2020, 00:03 (363 days ago) @ David Turell

Patterns of vascular structures are evolved efficiently:

"A new study shows how a wide variety of vascular networks can be created by changing only a small number of a network's attributes. Published in Physical Review Letters, the work of two physicists, former Penn postdoc Henrik Ronellenfitsch and professor Eleni Katifori, shows that vascular networks evolve through a tradeoff between how well the network can transport fluid, a network's "cost," or how many cells it takes to build the network, and its robustness, or how well the system works if part of the structure is damaged.

"This research builds off Katifori and Ronellenfitsch's previous work on "adaptation equations," mathematical models of systems that are good at a specific function, such as moving fluid. In this study, they wanted to see if their adaptation equation could get vascular networks to "self-organize" into the most efficient structure possible.


"When researchers want to analyze the costs and benefits of different trade-offs, they rely on a concept known as Pareto efficiency. As an example, in renovating a house with new insulation under a limited budget, one can either spend a lot of money and have a house that is well-insulated, or spend less money and do little to improve the insulation. The most efficient set of options, on the spectrum of low to high cost and from few to many renovations in the illustrative example, is known as the Pareto frontier. Using this approach, Ronellenfitsch was able to see which attributes were the most important to create efficient vascular networks. "The networks that we identify are those where you cannot improve any of these requirements without getting worse at one of the others," he says.

"The researchers found that vascular network efficiency was driven by how robust the network was to damage and how "expensive" it was to build. Across a spectrum of changes to these two attributes, researchers could create a wide variety of structures from intricately interwoven networks that were robust against damage to simpler designs that wouldn't stand up to breakage.

"But how does nature know how to balance cost with robustness? By simulating fluctuations, or changes in the average amount of fluid that moved through parts of the network, they found that changes in flow rates impact whether a network should be robust or not. "If you want something that is cheap but not robust, you'd better not have a lot of fluctuations," says Katifori.'

Comment: It takes a good designer to find just the right mix of attributes. It doesn't happen by trial and error, as proposed BY Darwin.

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