As an agnostic and seeker in Christ, despite modern science's decrees-
A)What would ever PREVENT the theory that single celled organisms took over "Everything;" if their existence predates the Cambrian period, what's to say that "Toxoplasmis....." or "Guardia Lamblia,"......, isn't literally "Controlling us" today, per the basic theories of science (IE-if I was to a "Revelation of Christ," and/or "Hear God's voice-" etc...whose not to say "These creatures" wouldn't be behind that part of everything else?
B)Per that of Creation Scientist's and accepted belief system, even if the "Ancient Lobsters exploded from pre-Cambrian single cells (Above)," why not one walking ape/monkey/human and/or whale/dinosaur, for that matter.
Hope the question makes sense....thanks for your volunteer time, Jeff.
Hey Kevin, good questions. I've divided my response into several sections and put links on the bottom of the page. I decided to answer question B first, so that way you can have evolution on your mind when I answer question A.
(B1) The Cambrian Explosion:
Your terminology “exploded” and “Cambrian” makes me think you are referring to the Cambrian Explosion, but your question seems to indicate that you may not understand how the Cambrian Explosion works. So I think this is the first place to start on this question.
The Wikipedia page is a great resource on the Cambrian Explosion and I was also able to find several blog posts by scientists describing it . Creationists are obsessed with the Cambrian Explosion so there is a lot of misinformation which has to be debunked . If you're interested in books about evolution in the Cambrian and pre-Cambrian I can recommend a few .
Allow me to explain the Cambrian Explosion in my own words. At Darwin's time, the earliest fossils came from the Cambrian period. The fossil record had to start sometime, but it was the larger variety of shell organisms that appears over a relatively short period of time (tens of millions of years) that was surprising. The earliest Cambrian fossils included small-shelly fossils, ancient snails and other unusual shelled organisms and another twenty million years later there are ancient sponges, ancient mussels, and trilobites/arthropods. If all these shelled Cambrian species came from a single ancestor that was the first to develop a shell adaptation, than the time span would be too short (or evolution too fast) to generate the variety of shelled organisms seen in this first part of the fossil record. Then it was a real mystery, but now that mystery has mostly been solved.
The first thing biologists realized was that evolution didn't have occur at a constant rate - it could occur a little faster or a slower depending on circumstances. For example, if there is a massive extinction event, then biologists have found (experimentally, computationally, and mathematically) that this encourages a subsequent period of rapid evolution. When the environment changes, organisms can adapt to that environment in different ways and those different strategies of adaption may eventually lead to different species.
But the major breakthrough in understanding the Cambrian Explosion came when modern methods enabled biologists to collect more fossils, preserve fossils better, and analyze fossils more thoroughly. The new techniques enabled biologists to collect soft-tissue fossils, so they didn't require shells or bones to see the fossil. They were also able to collect fossils indicating burrowing patterns that organisms left, again without requiring shells or bones. This new fossil data enabled scientists to identify the organisms that preceded the Cambrian called Ediacaran biota. Ediacaran organisms resembled flatworms and shell-less mollusks.
What biologists found was that the diversity of organisms before the Cambrian nearly matched the diversity of organisms after the Cambrian. So now a new idea for the Cambrian Explosion emerged – rather than one shelled ancestor rapidly evolving into many different shelled species, several different species independently developed shells during same hundred million year period. In this case, evolution wouldn't have to occur unusually fast, they would just have to explain why multiple species changed in the same way at approximately the same time.
A modern theory on the Cambrian Explosion indicates that the weather on Earth was especially torrential during that time period. Consequently, the sediments on the ocean floor would have been stirred up and the Calcium content of the water would have risen dramatically. Organisms need Calcium to make shells (calcium carbonate), so this Calcium-rich environment would have enabled species to develop shells for the first time and this would explain why different species developed them within the same time period. We know from contemporary experience (unfortunately) that marine invertebrates are quite sensitive to changes in the oceanic Calcium .
Oceanic Oxygen also increased during this time, which may have allowed new evolutionary adaptions. For example, data indicates the earliest predators emerged at this point (probably a flatworm). Before then, organisms only had to concern themselves with feeding and breeding. Once predation evolves, there is a natural selection effect that encourages other species to evolve defense mechanisms. Evolving a shell is the simplest defense mechanism. In the same period, the eyes of organisms evolved considerably as well. For an organism that just has to graze, high quality eyes aren't a priority, but predators and prey need to pay attention to each other.
(B2) Incremental Changes in Evolution:
So now biologists can identify possible causes of the Cambrian explosion, and the only questions that remain are to what extent each cause cauces actually contributed to the Cambrian explosion. There is no doubt that the Cambrian explosion preceded from incremental evolutionary processes over the course of tens of millions of years. Ancient arthropods (rock lobsters) could evolve from shell-less marine vertebrates, because they were similar enough already.
I think you should read more about evolution in general. Jerry Coyne's “Why Evolution is True” is highly recommended as a book about evolution that is both easily understandable and completely thorough in its description of evolution . I think it may answer a lot of questions about evolution that one might have. If you can't get ahold of that book (or want more), I'd also recommend Dawkins' “Greatest Show On Earth” , Shubin's “Your Inner Fish” , and Zimmer's “Evolution: Triumph of an Idea” . Of course there is Darwin's original Origin of Species which is still worth reading (he did not anticipate how much more evidence for evolution would come to light but he did anticipate creationist arguments). There are also plenty of free online resources on evolution, for example the National Center for Science Education  or this video series . There are also a couple of demos of evolutionary algorithms , in which a computer simulation demonstrates how variation, heredity, and selection lead to improved results over many iterations.
A low rate of mutation creates a natural variation of features in a population and each generation inherits its traits from a selection of the previous generation. Only some of that population will survive long enough to create offspring and some create more successful offspring than others. This selection effect ensures that the traits inherited by the next generation will be slightly biased towards traits that promoted survival in their parents. Human domestication of animals and cultivation of plants are an example of artificial biological selection. Nature can do the same thing, selecting for survival traits.
If the mutation rate is too low for a species, the variation in the population will be to low and a change in the environment (or a change in competing species) might cause the entire population to die out. If the mutation rate is too high for a species, it may ruin the survival chances of the next generation. A bad mutation may be very bad and a good mutation may be only slightly good, so net beneficial mutation involves minimizing the probability of a very bad mutation. A species also has to be close enough to its community to survive – its parents must be able to give birth to it, recognize it as their own, know how to raise it right, and (for sexual species) it must find a mate with which it can create a viable offspring. Evolution occurs in manageable incremental steps and it can only occur so fast. So this is the reason why a sea slug only needs tens of millions of years to evolve into a shelled sea snail but hundreds of millions of years to evolve into an ape. It seems remarkable that evolution can go from sea slug to apes in a very large number of very small steps, but the evidence describing this incredible journey is all there (again, I'd refer you to the books for details).
(B3) Evolution of Multicellular Organisms:
You asked specifically about the evolution of multicellular organisms. It may be hard to imagine how a transitional species between single-celled organisms and multicellular organisms might exist, but they do exist. There are several species in such a period of transition right now and evolution biologists study them to gain a better understanding of how multicellularity evolved in our single-celled ancestors. I recommend you read up on both Chlamydomonas and Choanoflagellates.
Describing how evolution works in this case is a little more complicated, because I have two explain two more key concepts of evolution – cellular differentiation and kin selection . Lets start with cellular differentiation. Multicellular organisms have many different types of cells that all share the same DNA. When you think about it, its quite remarkable that neuron cells, blood cells, and all the many other types of cells in the human body are so different from each other. These cells share the same DNA but the genes are “expressed” in very different ways to make these very different types of cells. This kind of cellular specialization is highly adaptive because its what lets us have organs and bodies .
Single-celled organisms can exhibit similar behavior but for different reasons. In a nutrient-poor region may require a different cellular strategy than a nutrient-rich region, and therefore its adaptive for a single-celled to exhibit features that depend on its environment. A colony of single-celled organized would then find that their cellular expression depends on their physical arrangement. Organisms evolving in such a context could depend on the specialization of their neighbors and therefore can evolve to become even more specialized. In the transitional form, the organisms are viable either as solo single-celled organism or when performing a specialized role as part of a colony. When the transition to multicellular is complete the organism can only survive as a colony and whenever it reproduces it builds a copy of the entire colony.
Thinking of a multicellular organism as a collection of single-celled organisms requires those single-celled organisms to be in a state of extreme dependence. For example, our skins cells routinely die to make room for new skin cells but this is unexpected behavior in independent organisms - its considered extremely altruistic to sacrifice one's life for another human. Moreover if organisms have traits selected for survival, it seems puzzling that self-sacrificial behavior could ever be evolved. The key is to think of traits being selected for the survival of that trait, genes selected for the survival of that gene . If I have a gene that makes me share food my children, it will be less food for me but it will help ensure by children survive and therefore maximize that the chance that gene would get passed on. The spread of such a gene is favored by evolution. My children would each share 50% of my genes, but so would be brothers and sisters. So if there's a gene that encourages me to help my brother, than there is at a 50% chance that would be helping propagate that gene. So it could be genetically adaptive to risk or even sacrifice my life to save my family. The more closely related, the more likely they are to share that altruistic gene, and therefore the more this gene would be spread when we help each other.
In the case of a single-celled organism, whenever it divides it creates a clone of itself. Single-celled organisms can form a colony completely out of (nearly) identical copies of itself. So any trait that ensures the survival of the colony could be evolutionarily favored even if it involves sacrificing individual members of that colony. I want to stress here, that this kind of “altruistic” cell behavior does not the cell to be able to engage in any moral reasoning or even be aware of what its doing. For a colony of single-celled organisms, this is every bit as natural as your skins cells dying to make room for new skin cells. You can read more about how cell death can promote the health of a colony and how this was evolved here .
(A1) Giardia Lamblia and Toxoplasma gondii
Giardia Lamblia does not control its host. Giardia causes symptoms, such a diarrhea and vomiting, but it does not control host behaviors. Giardia resides in the digestive system, not the nervous system, and so anything unusual host behaviors are a reaction to the circumstance rather than a direct manipulation. Compare it to the flu, for example. Influenza causes its host sneeze and cough, which then spread influenza to a new host. But these symptoms are involuntarily reactions to what influenza actually does which is cause inflamation of the respiratory system. Giardia is on the same level. Even when influenza causes feverishness, its actually that the body raises its temperature as a response to the flu and the side effect is that it causes the brain to perform poorly. There is nothing in the informational content of the flu, for example, which would affect how the mind reacts to the increase in heat.
So when we are talking about potentially mind-manipulating parasites in humans, we're down to Toxoplasma gondii. Acute toxoplasmosis causes an infection similar to influenza – swollen lymph nodes and general acheness. Except for people who have unusually weak immune systems, the human body fights off the infection within a month and may not even notice. At that point it may become latent, which means that the parasite is semi-dormant, immobile, and found in cysts in the brain. A history of toxoplasmosis (either permanent damage from the original infection or an effect from the latent stage) has been correlated with schizophrenia. Not all schizophrenics have a history of toxoplasmosis and not all those infected with toxoplasmosis develop schizophrenia.
Recently, there has been a lot of interest as to whether toxoplasmosis correlates with other mental disorders or personality traits. This was all started by some unaffiliated researcher named Flegr. There are a lot of papers claiming to demonstrate that latent toxoplasmosis has other mental effects on humans, but I do not come to the same conclusion because I think these studies were poorly done. For example, one can find a correlation between toxoplasmosis and reckless personality traits but “correlation does not mean causation”. Individuals who are reckless may be more like to contract toxoplasmosis in the first place and the studies do not account for that possibility. Humans contract toxoplasmosis by ingesting undercooked contaminated meat, by eating unwashed vegetable contaminated with cat feces, or by babies born to mothers with an acute infection of toxoplasmosis.st Perhaps individuals who are reckless are less likely to properly cook their meat or wash their vegetables. Maybe individuals who are extremely poor are more likely to purchase lower-quality foods that are more likely to be contaminated. Perhaps how often individuals cook or what they cook impacts their infection rate.
One could come up with another half a dozen reasons why personality traits might be connected to risk factors (instead of induced by the disease). Sadly psychology has a serious problem where observational studies have reported dramatic correlations between unrelated phenomena because they failed to consider the appropriate confounding variables. The initial poorly done study always gets more media attention than the subsequent study which debunks it. Psychology is not like physics and math, in which first publication results in relatively final. In psychology, confounding variables and publication bias make it so even well-done studies have to be replicated by a variety of different research teams and shown in a variety of different ways before they become settled science .
So I'm really not convinced that toxoplasmosis does anything other than cause temporary influenza-like symptoms and increase the risk for schizophrenia. And I don't believe it needs to manipulate human minds in order to cause either of those effects. But I also cannot rule it out as a possibility that toxoplasmosis also has impacts on human personality. Were that the case, one should still think of it as reaction that the brain has to what the parasite is doing and not the parasite exerting a conscious control over the brain.
Some researchers also believe that ordinary gut bacteria influences the brain. If we believe this result, it presents a mystery. The gut bacteria never directly interacts with brain, so how could that influence the brain? Think of the giardia and the flu. The body responds to the organism, the brain responds to the body. I think think that even in the case of toxoplasmosis, which actually resides in the brain, any effect it would have on the brain is of the nature – affecting the brain's environment in a broad manner, rather than controlling it on a neuron level.
(A2) Evidence against global mind-controlling single-celled organisms:
Now let me talk about the general idea that single-celled organisms could be controlling brains across the globe. The first thing to remember is that we can detect single-celled organisms. Toxoplasma gondii, for example, was discovered as early as 1908 and the first human case was found in 1938. Our imaging and diagnostic technology has increased dramatically since then. Now toxoplasmosis is detected with a simple blood test. So whatever is in our brains and bodies, science knows about it. There is no single colony of single-celled bacteria found in all humans. And multiple single-celled species working together makes no evolutionary sense. If there were any single-celled control or manipulation of human brains, the incidents would be isolated and follow no identifiable pattern across the entire human population.
The limitations of what parasitic control can do is limited to broad effects, rather than control of the mind. As a rule of thumb, parasites cannot do anything that you could not imagine a medicine, drug, or chemical doing to the brain. So it could be possible for a hypothetical parasite to make you thirsty, make you feel depressed, make your memory worse, make you talk louder, make you sleep later, make your testosterone increase, make your skin feel numb, etc. It would not be possible for a hypothetical parasite to make you hear a specific message, teach you skiing, make you assassinate a target, make you change your name to Borg, or give you a particular memory.
The reason why parasites can't do anything cognitively sophisticated is because they can't think, much less read thoughts, much less control thoughts. Thinking requires a neural complexity that small organisms simply lack. One could perhaps imagine many single-celled organism signaling to each other in order to think, much like our own neutrons coordinate to think. But groups of single-celled organisms don't think either. For one thing, our neurons are cells which are very specialized for signal transmission. Their long and branching and they have just the right activation threshold. If there were any single-celled organisms signaling in a similar manner, this fact would be immediately obvious just by looking at them under a microscope.
Furthermore, there would still need to be brain-sized number of single-celled organisms in order for them to be capable of deliberately controlling our thoughts, planning, understanding, memories, etc. or having that of their own. Such a large concentration of single-celled organisms would be obvious in a brain autopsy and probably also obvious in MRIs and CAT scans. If that were true, we literately wouldn't even be able to describe how the brain works without referencing its interaction with the massive bulk of single-celled organisms residing in it.
(A3) Single-celled parasites make for a poor God:
If we assume from the start that these organisms are guided by a divine plan, than we've already assumed the existence of God and there is no need to talk about these organisms playing the role of God (because God could play the role of God). It'd be circular reasoning. So its really only enlightening to assume that these organisms are a product of a natural godless universe and see if we can imagine organisms in such a circumstance playing the role of God.
In absence of God, the development of these single-celled parasitic organisms would be guided only by evolution by natural selection. So the concerns of these organisms would only be surviving and propagating themselves. If we look at this (dramaticized) list of real world parasites , we see the presence of the parasite revolves around perpetuating its life cycle. If humans were controlled or manipulated in any significant part by parasites we'd become obsessed with unsanitary behaviors like eating contaminated foods and contaminating the food others will eat. Its hard to see how anything divine might arise out of that.
(A4) Scientifically Possible vs. Scientific:
It sounds like your goal here is to find a view of God that science hasn't shown to be impossible. I would say it doesn't matter whether God is possible -it matters whether God is probable. Because to conclude God is possible means nothing. Everything is possible. Even things that violate the laws of physics are possible, because its always possible that we don't perfectly understand the laws of physics. Even atheists think God is possible , but that doesn't mean we should act as though it were true.
As I explain to Branden in a previous post , the problem with miracles is not that they violate the laws of physics but don't pass scientific criteria for a plausible theory of how the universe works. I am also reminded of my post on “Exodus Decoded” a convoluted (and highly inaccurate) attempt to explain the book of Exodus as within the realm of scientific and historical possibly. Scientific theories require evidence and are able to not only describe but explain the natural world. A hypothesis needs to be scientifically possible, but if a hypothesis doesn't have evidence to support it than its just a hypothesis.
Let's try to estimate the possibility that bacteria are controlling the world according to the whims of God. Let's say the chance of all the world's single-celled organism coordinating their efforts to be 1%. And the chance that these single-celled organisms are organized in such a way to have sophisticated control of our thoughts to be 1%. And the chance those single-celled organisms direct their efforts in such a way to resemble the will of a god to be 1%. Since we don't have evidence for any of these things occurring and have evidence against them, I suspect the actual probabilities would be far less. But for the sake of argument, let's say the probability this idea is right is approximately a one in a million chance (0.01*0.01*0.01). I think it would be unreasonable to believe in such an unlikely but possible God. No defendant would be convicted on a one in a million chance of he's guilty. No one would vote for a politician who claims a one in a million chance his or her policies will succeed. No one agrees to a surgery that has a one in a million chance of survival.
The reason why I emphasize this is because before I became an atheist, I was afraid to become an atheist. I latched on to any tenuous reason to believe in God and invented all sorts of convoluted ways to make the natural world fit with God. What made me become an atheist, finally, was not any new fact I learned about how the world work. It was when I decided I wanted to know the truth more than I wanted to keep making excuses. It would only be much later before I realized that an atheist wasn't such a bad think to be. So I hope you realize that its okay if God doesn't exist.