The observation of repeated occurrences of convergence in the history of Earth’s life stands as a profound challenge to naturalistic explanations for Earth’s life.1 Now, another recently recognized and especially dramatic occurrence of convergence2 provides yet another challenge to naturalism and support for the biblical creation model of life.
Convergence refers to the occurrence of identical, or nearly identical, anatomical, physiological, and/or genetic features in species of life that are unrelated or distantly related within an evolutionary paradigm. Both theists and nontheists offer explanations for convergence, but those explanations are radically different.
Theists see convergence resulting from supernatural, super-intelligent interventions by a single Creator who employs a single, optimal solution to address a common set of problems faced by organisms possessing different characteristics and living in different habitats. Nontheists conjecture that convergence occurs when unrelated species encounter identical, or nearly identical, environmental, predatory, and/or competitive selection effects. In other words, nontheists suggest that natural selection channels randomly occurring variations in unrelated species toward identical outcomes.
There are two obvious problems with the nontheistic explanation for convergence. First is the frequency with which it is observed to occur. Naturalistic models for Earth’s life predict convergence to be extremely rare. Instead, convergence is a nearly ubiquitous characteristic of Earth’s life. So far, hundreds of examples have been documented.
Second, evolutionary biologists, paleontologists, and ecologists frequently observe occurrences of convergence where the environmental, predatory, and competitive selection effects are not at all similar. A classic example is the chameleon (a reptile) and the sand lance (a fish).3 The chameleon lives in a desert while the sand lance lives on the seafloor of shallow seas. The chameleon faces very different predatory pressures than does the sand lance. Yet, both the chameleon and the sand lance possess identical eye, eyelid, and tongue mechanisms as well as designs and identical hunting strategies.
The most recently discovered example of convergence is the centralized nervous system found in all vertebrates and insects. The materialistic model asserts that the centralized nervous systems evolved from a single common ancestor.
Evidence that could be interpreted as favoring the naturalistic model comes from the observation that all vertebrates and insects possess a nervous system consisting of a brain that is connected to a single cord of nerves that extends into the trunks of these animals. Furthermore, regulatory genes are similarly deployed during the development of the central nervous systems of these animals.
However, the new convergence discovery provides strong evidence that central nervous systems do not arise from a single common ancestor. Rather, there were multiple independent initial appearances of central nervous systems.
A research team led by marine molecular biologist José Martin-Duran found that a set of homeobox genes is expressed along the back-to-belly axis of the central nervous systems of vertebrates, flies, and one species of segmented worms. However, the team did not find this gene expression pattern in nine other bilaterian species (species with bilateral symmetry that possess a head, a tail, a back or dorsal, a belly or ventral, and a left side and right side).4 Four of the nine species were members of the xenacoelomorph phylum comprised of tiny worms that lack a through gut, gill slits, and a body cavity. The other five were members of the annelid (segmented worms), nemertea (ribbon worms), brachiopod (soft-bodied animals with shells on the upper and lower surface), platyhelminth (flatworms), and rotifer (part of the zooplankton) phyla.
The team concluded that “the similarities in dorsoventral patterning and trunk neuroanatomies evolved independently in bilateral.”5 In a review of the paper published by Martin-Duran et al., neurobiologist Clifton Ragsdale wrote that the team’s data “strengthen the case that the developmental and morphological similarities between bilaterian centralized nervous systems are the result of independent evolutionary events that converged on similar outcomes.”6 In other words, central nervous systems did not arise from a common ancestor through evolutionary descent. They appeared independently multiple times.
What makes this example of biological convergence especially significant is its occurrence across phyla. It is not just convergence within an order, class, or phylum. It is observed in at least eight different phyla. Biological convergence repeatedly arising in circumstances where the forces driving natural selection are vastly different strongly argues for the compelling necessity of supernatural, super-intelligent activity on the part of a personal Creator.
Featured image credit: Field Museum, Chicago