A foundational idea of evo‐devo is that morphological variation is not isotropic, that is, it does not occur in all directions. Instead, some directions of morphological variation are more likely than others from DNA‐level variation and these largely depend on development. We argue that this evo‐devo perspective should apply not only to morphology but to evolution at all phenotypic levels. At other phenotypic levels there is no development, but there are processes that can be seen, in analogy to development, as (...) constructing the phenotype (e.g., protein folding, learning for behavior, etc.). We argue that to explain the direction of evolution two types of arguments need to be combined: generative arguments about which phenotypic variation arises in each generation and selective arguments about which of it passes to the next generation. We explain how a full consideration of the two types of arguments improves the explanatory power of evolutionary theory. Also see the video abstract here: https://youtu.be/Egbvma_uaKc. (shrink)

A replicator is simply something that makes copies of itself. There are hypothetical replicators (e.g., self-catalyzing chemical cycles) that are suspected to be unable to exhibit heritable variation. Variation in any of their constituent molecules would not lead them to produce offspring with those new variant molecules. Copying, such as in DNA replication or in xerox machines, allows any sequence to be remade and then sequence variations to be inherited. This distinction has been used against non-RNA-world hypotheses: without RNA replication (...) systems have no capacity to exhibit heritable variation. However, is copying the only way to have heritable variation? This article suggests that evolution can happen without anything being copied and that, in fact, RNA copying is too complex to arise spontaneously as the first pre-biotic system. There would then be a historical gradation of systems from non-alive to alive in which the capacity to have heritable changes would progressively increase and in which copying, as in template-based RNA-replication, would be a crucial but relatively late event. In addition, this article proposes a way by which RNA replication could have arisen, after systems able to evolve arose, as a crucial innovation and how that innovation spread over existing evolutionary systems and became a major driver of subsequent evolution. (shrink)