Sodium (Na) is an element that often has a plus sign (+) next to it depicting the fact that it has a positive charge. Each element in the Periodic Table has a definitive set number of protons, neutrons, and electrons. Elements in their ionic form are not in their most stable form until they complete their electron valence shells, which occurs by either giving up or grabbing onto electrons from other elements.
Sodium has 11 electrons:
- 2 in its first energy level (1s2)
- 8 in the second (2s2 2p6)
- 1 in the outer energy level (3s1)
Sodium is found to be a positively charged element as a result of being short one electron. But Sodium is not stable with one lone negatively charged electron spinning around in its outermost level, so Na will always give up its outer electron whenever possible. By doing so, energy level 2 becomes the outermost energy level, and exhibits stability with its complete set of 8 electrons. This electric property assists in making sodium (Na) an important element in neuron activity and nervous systems in life forms.
Nervous systems and their component neuron cells are a key innovation making communication possible across vast distances between cells in the body, sensory perception, behavior, and complex animal brains.
Researchers from the University of Texas at Austin led by Harold Zakon, professor of neurobiology, and Professor David Hillis coauthored a paper along with graduate student Benjamin Liebeskind that was published in PNAS in May 2011. Zakon notes, “The first nervous systems appeared in jellyfish-like animals six hundred million years ago or so.” In order for nervous systems to be possible, their precursor sodium channels would have had to been in place prior to the development of jellyfish. Zakon confirmed, “We have now discovered that sodium channels were around well before nervous systems evolved.”
According to the University of Texas at Austin press release, sodium channels are an integral part of a neuron’s complex machinery. Sodium channels are described to be “like floodgates lodged throughout a neuron’s levee-like cellular membrane. When the channels open, sodium floods through the membrane into the neuron.” This generates nerve impulses, and from there complex nervous systems can be derived, all because of the seemingly infinite potential electrical applications that can be derived from the positive charge of sodium molecules.
The Univ. of Texas research team discovered the genes for such sodium channels hiding in a primitive single-celled organism, a choanoflagellate. Choanoflagellates are Eukaryotes, the supposed evolutionary ancestors of multicellular animals like jellyfish and humans. It’s interesting to note that not only are choanoflagellates unicellular, but they have no neurons either.
The press release further states,
Because the sodium channel genes were found in choanoflagellates, the scientists propose that the genes originated not only before the advent of the nervous system, but even before the evolution of multicellularity itself.
Sodium channel genes are complex. The Univ. of Texas research team illustrates such a gene in their PNAS paper here:
The image above is Figure 1 in the PNAS paper, which is a hypothetical rendition of secondary structure of a sodium-channel protein. Transmembrane domains at the top (DI–DIV), their component segments (S1–S6), and their connecting loops (in white) are in view. The pore loops (P loop), which dip down into the membrane, form the ion-selectivity filter. The inactivation gate resides on the long loop between DIII/S6 and DIV/S1. The middle section illustrates how the domains cluster to form the protein and its pore. The lower section displays the fine structure of one of the domains with the pore loop in the foreground. The black dots on the pore loops in the (Top) and (Bottom) represent the location of the amino acids, which makes up the pore motif.
In this image immediately above, the research indicates that the sodium channel protein is highly conserved in that it existed at nearly the highest known taxa level within the Eukarya domain. In other words, it’s essentially always existed from the very earliest beginning of the domain Eukarya.
In another study of sodium channels published in Physiological Genomics (May 2011), Swiss researchers reported the same conclusion. The story was featured in both Science Daily and PhysOrg exclaiming, “Fluid equilibrium in prehistoric organisms sheds light on a turning point in evolution” as the captioned title.
The Swiss team researched how sodium channels help solve the problem for primitive cells that cannot pump sodium out of their membranes effectively. The inability to pump sodium was an evolutionary roadblock. Bernard Rossier (Univ. of Lausanne) figured out how the problem was solved. A certain subunit of a gene for pumping sodium suddenly “appeared” out of nowhere, and the rest was history.
In humans, the sodium channel protein (ENaC) traverses a cell’s membrane and facilitates the movement of salt into and out of the cell. ENaC is regulated by the hormone aldosterone. The Swiss researchers found that ENaC and Na, K-ATPase, an enzyme that also plays a role in pumping and transporting sodium, were in place before the emergence of multi-celled organisms.
When tracing the alpha, beta, and gamma subunits of ENaC back, the Swiss “team found that the beta subunit appeared slightly before the emergence of Metazoans (multicellular animals with differentiated tissues) roughly 750 million years ago.”
Rossier was unsure as to when the emergence appeared. Dr. Rossier said that although it is possible that the genes for ENaC originated in the common ancestor of eukaryotes and were lost in all branches except the Metazoa and the Excavates, there is another possibility. There could have been a lateral transfer of genes between N. gruberi and a Metazoan ancestor, one that lived between the last common ancestor of all eukaryotes and the first Metazoans.
While both studies by the Univ. of Texas and Swiss teams use phylogenetic trees to examine the evolution of these highly conserved proteins and enzymes, the fact is clear that these biochemical systems and complex cellular machinery have been highly conserved and present in species from the earliest dawn of the beginning of the Eukarya domain. This being the case, the fact that these highly complex systems were required for eukaryote evolution to be possible, and existed from the very beginning of Eukarya cells, the evidence is more supportive of Intelligent Design theory than known mechanisms of evolution.