If I only had a brain! Sea anemones claimed as a brainless ancestor!

An article on recent genetic studies of the simple sea anemone, in this case Nematostella vectensis, show that the genes involved in the development of the human head (and other animals with heads) are present in this creature even though it has no head.  These genes help produce one end of the animal which was once thought to be the foot.  This interesting part of the little beast has tentacles and a mouth but no true head. 

Headless and in fact brainless, the foot of the anemone is the "head" portion of the animal according to the activity of genes involved in developing this part of the animal.

Headless and in fact brainless, the foot of the anemone is the “head” portion of the animal according to the activity of genes involved in developing this part of the animal.

According to this recent article, this information points to the evolutionary origin of our own head.[i]  Although the article does not say how this points to an evolutionary association, it is commonly assumed that the anemone is one of the branches of the animal ancestry that supposedly gave rise to all higher animals including ourselves. “Sea anemones and all higher animals, including humans, share a common brainless ancestor which lived between 600 and 700 million years ago”, according to Science Daily.  No one has ever proven this lineage or evolution for that matter and the sea anemone genes that share so much identity with the genes that control the development of our head during our embryonic gestation may have absolutely nothing in common with evolution of heads.  An important piece of information is that the anemone has two life forms, a larval and the adult form.  One particular gene (six3/6) is only expressed in the development of the larval form.  Higher land animals like reptiles, birds and mammals do not go through a larval form of life, though many insects, and amphibians do.  This distinction is important when one begins to toss out stories on evolution.  It would not be fair or meaningful to suggest we are the product of the larval form of the anemone ancestor but this should be the implication.  What is even more fascinating at the molecular level is that though this gene, called the bilaterian anterior developmental gene six3/6, is found throughout the animal kingdom, it plays no part in the construction of the anemone’s head since this creature has none.  Also, Homo sapiens are supposed to be 700 million years removed from the common ancestor of this creature, and yet our six3/6 gene says otherwise.  When we compare the protein sequence (linear arrangement of amino acids that make up the protein) we find 87% of the sequences share identical residues.  The figure below (Fig. 1) shows the two sequences, one from man (Homo sapiens) and the other frm anemone and the middle sequence is a composite or consensus sequence of what most would consider the necessary amino acids (also called residues) that should  theoretically conserve the function of the protein.  The Query is the sequence taken from the sea anemoneThe Subject is the protein’s amino acid sequence from the human gene.  The similar amino acids that are shared between the two proteins are in black in the middle row.  You will note that the human sequence starts with 82 residues into the sequence meaning 82 extra residues belong to our gene and not to the anemone gene.  Of the 191 amino acids that line up, the middle sequence in black shows the composite or consensus sequence between the two proteins.  Some sequences don’t agree at all – but these are very few (13 residues show a blank, meaning the protein does not compare at these sites.  The + sign means a residue on one chain is replaced by a residue of similar properties on the other chain.  Overall 93% of the protein sequences match with the exception of the 82 residues missing on the anemone’s gene. This is fascinating! The gene’s product, these proteins, is nearly identical between the two species after 700 million years of “evolution”.  Molecular evolutionists would call the protein “highly conserved” among the animal world.  This means natural selection does not permit many modifications to the gene because they are deadly.  The sequence is therefore kept from changing over time.  The point being that any significant change would be lethal and so mutations of the gene sequence are not retained through time. 

Amino acid alignment of two proteins from the Six3/6 gene.

Amino acid alignment of two proteins from the Six3/6 gene.

Is there another way of looking at conserved genes?  Many other proteins that are vital to fundamental cellular functions found in respiration, protein synthesis and the folding and target location of molecules within the cell are not conserved.  In some cases the gene has, in evolutionary theory mind you, mutated 80% from the original molecule but retained similar structure and retained the same function due to amino acid substitutions of the same kind of amino acid.  That is, if an amino acid is charged with a positive charge, the replacement is a positively charge amino acid.  Overall, the entire sequence can be very different from one species to another species but the actual shape of the molecule is what is conserved, not the linear arrangement of residues that made the proteins.  Why this didn’t happen with the six3/6 protein is very unusual especially given evolution’s claims and near identical protein sequence between man and anemone.  Even more amazing to me is that after 700 million years the poor little anemone is still headless and brainless. What were the selective pressures that one day led to more genes, different genetic controls, and ultimately a horrendously complex coordination of molecular and cellular events that created the first head? [What a strange question even to ask!!!].  If having a head is advantageous why doesn’t the anemone have one?  If not having a head is ok, then why did evolution select for one?  Should we believe this story?  Is it just as possible that proteins represent tools from a toolbox of such molecules and that the intelligent selection of the right proteins used to create a living creature has been made by design to assure that the critter or plant is replicated over and over and over again with precision?  This has as much support and is as valid as the story told by other scientists who have no proof of the evolution of the head or the ancestry to anemones.  By assuming evolution, and assuming some relationship to anemones one can claim whatever feels good.  Is this science?  The paper describes the development of the anterior end region of the organism (once thought to be the posterior or “foot”) and shows that this protein when produced regulates other genes for the ultimate coordinated control of the development of the “head” region of the anemone.  Our own version of the gene has not changed much save for the additional sequences that appears to have no known function at the writing of this post.  However, damage of this gene in the developing human results in the failure of the developing frontal lobes of the brain to separate into two halves. This has major effects on facial development resulting in the loss of bilateral symmetry of the face.  If birth occurs the child typically does not survive.  It is born with a single eye, no nose, misplace ears and no true mouth.  Other defects of the gene impair vision and other sensory systems.

Genes represent the tools in a toolbox.

Genes represent the tools in a toolbox.

While the gene does make a similar if not the same protein in the anemone to regulate one end of the animals body, without a head, brain, eyes or other similar features typical of animals with a head, it is a stretch to suggest that somehow we have found a link to how the animal head evolved. It is imaginative but no real substance is found by suggesting the existence of the protein in a more “primitive” animal is a clue  to how evolution works. The authors of the paper had this to say: “By revealing the function of “head genes” in Nematostella, we now understand better how and from where the head and brain of higher animals evolved,” Sinigaglia and Rentzsch explain. I am not so easily convinced that revealing what this gene does in the anemone helps us in any way to comprehend where our heads came from.  Only that the gene is needed for both animals to develop apparently different things.  Is this evolution?  Did this paper actually add to the body of information we have on evolution?  It actually seems to have created far more questions than answers. 



[i] Chiara Sinigaglia, Henriette Busengdal, Lucas Leclère, Ulrich Technau, Fabian Rentzsch. The Bilaterian Head Patterning Gene six3/6 Controls Aboral Domain Development in a Cnidarian. PLoS Biology, 2013; 11 (2): e1001488  

Leave a Reply

Your email address will not be published. Required fields are marked *