Scientists now have their hands on the genome of the starlet anemone, Nematostella vectensis . This genome is important because it, in conjunction with other sequenced metazoan genomes, gives us a better picture of the last common ancestor of all animals. And as might be expected by now, the plausibility of front-loading evolution is enhanced.

Biologist PZ Myers is a hardcore critic of ID, yet nevertheless, his commentary on this research nicely fits within the context of front-loading (as explained in The Design Matrix). Consider some of his observations:

One of the general conclusions of the work with Nematostella is that, in a slap to our egos, humans are actually fairly primitive in gene structure and organization, and retain many more genetic attributes of the last common ancestor of the metazoa than do flies — flies are looking ever more radical and weird, the fast innovators of the multicellular world.

Another way of stating this is that human gene structure and organization was fairly well represented in the last common ancestor of all animals. Does this mean humans were front-loaded? No. But it is consistent with the view that facilitation for human-like complexity was at least partly in place.

The authors pulled out members of gene families that were found in Nematostella and were also found in one or more of the fly, nematode, human, frog, or pufferfish genomes (that list is unfortunately heavy on the vertebrates, but that’s what we’ve got to work with right now—we need more diverse genomes in the databases!). They identified a total of 7,766 ancestral gene families. The ancestral gene would have expanded by duplication events in each lineage, so that represents 12,319 genes in modern Nematostella and 13,380 genes in modern humans, or that about two thirds of our genes are straight out of the ancient metazoan toolbox, and less than one third, in both the anemone and us, are later additions.

These two thirds have thus played a crucial role in shaping subsequent evolution, such that significant amount of information for making something akin to flies, nematodes, humans, frogs, or pufferfish was already present in the last common ancestor. As explained in my book, this is the type of set-up that would help guide the blind watchmaker.

Individual lineages lost genes during evolution, so the estimate of the ancestral metazoan genome is very rough and is an underestimate. If an ancestral gene had been lost in the anemones, for instance, but had been retained in vertebrates, it would not appear in their tally. The ecdysozoan lineage, represented by flies and nematodes, seems to have been particularly prone to lose genes over their history. Out of those ancestral 7,766 genes, both flies and nematodes have lost 1,292; those genes are shared in anemones and vertebrates, but not in flies or nematodes. In contrast, the vertebrate lineage has lost 33 of the 7,766. We’ve been relatively conservative in retaining genes, while the ecdysozoa have been paring their genomes down.

Here, we can begin to appreciate the significance of front-loading, where something like a human genome was within closer reach to the genome of the last common ancestor, while other forms of evolution have been associated with loss of this complex state.

Myers then summarizes other ways in which the human genome is more like the starlet anemone genome and then hits on something that may indeed be a true echo of front-loading:

In another example of the conservative nature of evolution, the authors categorized the origin of eumetazoan genes. It is no surprise that 80% were ancient in origin, appearing before the origin of the metazoa. We are just glorified bacteria, after all, and most of what our individual cells have to do is identical to what yeast have to do.

15% are unique to animals. That just means that no homologs have been found in plants or fungi or ciliates or bacteria … but most of those genes are probably also very old, and evolved in the single-celled ancestors of the metazoan line.

2% are modified versions of ancient genes that have an added, novel domain.

3% are constructed by fusions and domain shuffling of parts of ancient genes to make a new hybrid.

The diagram below illustrates one example of a collection of genes that make a functional part of one signaling pathway. What we can see is that it isn’t as if novelty is discrete, that you will find a new gene doing something entirely, radically novel in cell function — instead, they tweak extant networks of genes to refine the capabilities of the organism.

Refining pre-existing capabilities of organisms is just another way of looking at front-loading, where it is the front-loaded state that does most of the evolutionary “work.” Of course, the key is found in the genes that are apparently unique to metazoans, as Myers describes them as “enriched for genes involved in signal transduction (like the example cartooned above), cell communication and adhesion, and a catch-all category of developmental processes, which includes genes involved in the emergence of the nervous system and in differentiation of mesoderm.” Where did these genes come from? Were they front-loaded to appear? Or did they simply appear by chance?

Whatever the answer, it is increasingly clear that cellular and genetic architecture of the the last common ancestor all animals imposed a rather robust boundary condition on subsequent animal evolution. Rewind the tape of life to this ancestor, and let it play all over again, in there is no good reason to think the animals that would evolve would be all that different from anything we see today.

So let us thus end with an insightful summary from Myers:

I take a broader view. I think it’s true that, as this work shows, multicellular animals are the product of fundamental genetic structures that were almost entirely pioneered by our single-celled precursors—we are bacteria writ large and sloppy. We also possess an amazing degree of unity within the various metazoan lineages; when we examine a sea anemone and a human at the genetic, biochemical, and molecular level, it’s easy to get overwhelmed with the commonalities at our foundation. We’re all the same in so many ways!