I'm trying to trace the path from early complex life to here. Its obviously not an easy thing to do but it is immensely interesting.

What started me in this particular interest is, in addition to my interest in evolution of eukarotes, I wanted to understand how the various aspects of the immune system arrose and how tissues organise together. I've come to think that the immune system is very important in tissue organisation and there must have been an immune system present long before other complex systems like brain tissue. Having started with neusoscience as an interest, and neural-immune interactions, it naturally follows it will be revealing to trace the parallel symbiosis of these different tissues as they develop.

There are lots of models that can be used, sponges are amongst the simplist life forms in the eukaryotic domain, amongst the earliest animals, and they already have a lot of immune systems in place which can be traced up to us.

They dont have recognisable neural tissue, being a very simple arrangement of a few cell types in layers, the sponge is a filter feeder that relies on dead organic material, but would none-the-less need a lot of immune capability to deal with the huge intake of potentially pathogenic organisms.

Theories on the foirmation of eukaryotes have taken me down different paths. I have worked on two models, one which might resemble a fungal creature that begins to evolve an increased ,metabolism, and the high metabolism of animals actually comes from trhe larval stages, and another less wacky idea of a filter feeder living in hydro-thermal systems or off algea drifting about.

I had a belief that the first animal was in fact predating that and lived off off bacteria in hydrothermal systems and dates back earlier than yet believed, but that is just a hunch. Anyway, the sponge is a filter feeder with a lot of features that make it worth looking at as a formative eukaryote, and the filtering method would need certain mechanisms to control pathogens. First up, any multicellular creature will need to defend itself from prokaryotes right at the beginning. By feeding off of the hydrothermal vent or away from major areas of photosynthesis, the first eukarotes could eat their prey by a process of cellular phagocytosis, just like immune cells. They would need to be abler to deal with all organisms, but by controlling energy supply, this would diminish the growth of the pathogen.

I reasoned that the first eukaryotes were dependent on controlling nutrient access thus could support less aggressive 'skins' of good microbe which could provide nutrients in return to whaty the larger structure of eukaryote could supply. This m,eant that nutrient supply and regulation was the key initial defense in my thinking.

So, anyway, it has been recently found from genetic analysis, that all the nasty major bugs surveyed by the experimenters, alive today, including herpes simplex family, go right back to very early evoltion and apparently to vent sites. This is a very compelling finding, because it shows that we are both highly adapted tyo each other. Human pathogens have most likely been plagueing us since before we were sponges!

Apart from the data I have found, which is very interesting and I intend to post it here at some stage, I have been trying to find data to supprt a hypothesis - that phagocytising immune cells, not only date back toi the earliest complex life organisation, and probably predated it, the early predation of large cells probably is what allowed the first pathogens access, and secondly, led to most of the orgamnelles in the eukarytic cell. The phagocytising immune cell needs a 'brain' to regulate what it eats in the first organism, so it doesn't eat differentiated, specialised cells. Remarkably, hints of such a system are found already in sponges, but that is spongething to be expected. So, this 'smart-immune cell' I also have started to suspect has the power, at an early stage, to control tissue growth and especially regrowth. The need to escape sources of damger al;so would lead onto a need for sensor cells of the immune system to affect a physical change in position, thus the origins of an actual brain and neuro-vasculature/musculature, with common features.

The smart immune cell in humans - i.e. dendritic cells - have the feature of identifying first damage, then immune responses. These smart macrophages (eating cells) then control the immune system. The key is that identifying damage is the same thing that pain nerves do. The similarity of neurons to dendritic cells escapes no-one - they were so named because of their dendritic cell like apendages. They also can form veils instead which allows them to ingest particles from outside. This may originally have evolved at such an early stage in eukaryotic life, maybe even predating it I wonder?

The technology of dendritic cells therefore, my thought is, date back to a common ancester to neurons and to current dendritic cells and B-cells amongst others. Both wings have diverged and spoecialised, but my thought is that neurons once were like dendritic cells and they possess a cell type ancesteor.

They now both contain a number of shared features.

Of course, this is alll much to obvious for scientist at present. Despite spotting the similarity of the two cell types, it is seen as too simplistic to even propose their relatedness. As yet I have found no evidence of why they are not. Stem cell precursors tell us nothing because this origin of mature cells from particular proginitors can switch readily during species evolution and because it varies depending on the tissue (apparently what proginitors are available).

One of the things that I did read was that dendritic cells are not neurally related, they are just 'rare cells in the skin'. Well, thats not much of an argument, because where do the brain cells come from? how are neurons arranged in the brain? They grow on layers of skin based on the neuroepithelial tissue/blood vessel walls.

The earliest brains were 'nerve nets' arranged on folds of skin, that activated early muscles. It should also be recalled that in the sponge, there are early cells that appear to be the origins of myocytes. Right there in the sponge, forming part of the structure of the sponge - its skin, is what? Phagocytising cells connected to flagella. I think these may well have been the origins of the central animal immune cells.

What this wqould mewan is, that according to the theory I am developing, we can interpret that early evolution led with phagocytosis in static cells in the skin of the sponge or sponge like organism, which had the power to initiate cascades that could lead to movement away from dangers or to better food. This is the orgin of all neuro-motor systems! The phagocytising cell is closely linked to, or the precursor of key immune cell capabilities like dendritic cells.

Because it would need a recognition and defense system, it would identify foods and threats alike, and be the ideal central point to collate data for both motor activities, and before that, immunal responses.

Yes, sponges can move several millimeters per day. Light, chemicals, who knows what triggers it, and how they do it.

There's alot of links to add in but bear with me.