Independent nanotechnology information and commentary since 2003
"Humans do it, bacteria do it, even viruses do it," reports Nature. Now, robots can be masters of their reproductive domains. But will Lord Broers believe it? (One thing for sure, I just asked for it.)
5/13/2005 04:42:00 AM
Why does the phrase "Stupid Robot Tricks" come to mind. The one on the left looks a little worse for wear. Now they need to get the robot that the robot built to build a robot.
More important than the stuid robot tricks is the authors' definition of self-replication:--------------------We circumvent the long-standing hurdle ofwhat counts as self-replication by suggestingthat self-replicability is not a binary propertythat a system either possesses or not, but is acontinuum dependent on the amount ofinformation being copied. This factor can bemeasured by comparing the log probabilityof a machine spontaneously appearing in anenvironment to the log probability of itappearing, given that one instance alreadyexists. This factor can be computed preciselyfor some well-defined formal systems13 andapproximated for others. For example, anabstraction of Penrose’s replicating tiles11yields a factor between zero (not self-replicating)and log 2.Even without calculating absolute numbers,systems can be ranked by comparingproperties that affect this factor, such as thenumber of basic building blocks used comparedwith the number of building-blocktypes and their complexity. This factor isexceedingly high for animals, which haveabout 1020 amino-acid combinations ofroughly 20 amino-acid types, but is very lowfor our robots (four modules of one complextype). This view allows us to quantify,compare and systematically improve the processesof self-reproduction. It is possible, forexample, that self-reproducing machinescomposed of many identical microscalemodules would improve this factor.Although the machines we have createdare still simple compared with biological systems,they demonstrate that mechanical selfreproductionis possible and not unique tobiology. . . .
I think the evolutionary concept of 'fitness' is a better quantitative measure of the ability to self-replicate.In a environment where multiple types of organisms compete for scarce resources, the organism which generates the most progeny (in the long run) is the most fit.
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