I think it probably went like this: a new feature (hard shells) was discovered by evolution, which gave so much advantage that all sorts of varieties could coexist for a while (even sub-optimal ones, as they still had the advantage over old organisms). Eventually, some winners among the organisms emerge, the advantage disappears and the sub-optimal variations begin to die out.
I like to compare it to the evolution of computer games. When they became viable first (home computer revolution), an incredible amount of games was developed. Eventually doom arrived on the scene and every game became a 1st person shooter. (Simplified story, of course). Or the dot com boom maybe - for a while, money was thrown at everything internet related. After a while some winning concepts emerged, and most of the contenders went away again.
One thing to keep in mind is that hard shells are much better at producing fossils. We don't have as good of an idea of how animals looked before the Cambrian or how diverse they were because most of them did not fossilize very well.
One thing that bugs me a about the discussion of evolution in general is it tends to get treated as a smooth process influence mostly by the environment but DNA is essentially digital code for building bodies and probably the Cambrian was kicked off by some mutation a bit like a code refactor that allowed a lot of body variation subsequently by the changing of a few base pairs.
A bit like, in a loose analogy the old code was
print "protein"; print "protein"
and the new code was
for i=1 to 2 {print "protein"}
so that in the second case a single mutation in the "2" could result in a wide variety of body sizes.
The reason why the Cambrian was considered special and was often referenced as an "evolutionary explosion" was because the pace/rate of speciation is abnormally high during that period only.
If you take your hypothesis for example, it may explain the explosion (rapidity) of the evolution of new species but it still doesn't offer viable reasons why the explosion was isolated to that period only.
(Just an amusing side note: my God-believing and evolution-denying BIL uses the evidence of the Cambrian explosion to suggest that no scientist can explain why there was an explosion of diverse species is such a short time - it had to be "God's hand". "Only a creator can do such a thing". I must admit, until the arrival of my BIL, the Cambrian period was of mild interest to me. I now read about it with "special interest".
He uses the very same evidence of the existence of the explosion and the absence of evidence to explain the explosion part of the evidence as reason to believe that "it is God". I usually end the dinner conversation when I keep asking "how?". On some very rare but weaker moments he might trip and admit "I don't know". At which point I end it by saying, that's a very scientific thing to say. :-)
Taking as an axiom that God exists and loves us, we can deduce that God wants us to be free because you do not want someone you really love to be your slave. If there was a way to prove the existence of God, we would not be free to believe or not. As a result, if "God exists and loves us", there is no way we can prove he exists.
I think the axioms you need for this kind of argument is that: is God exists, God is human-like, and God loves us.
Why would a cosmic being care more about humans than bacteria? Why would he value things like freedom over slavery? Why would he care if we believed in him or not?
> Those are entirely human qualities and concepts.
These are entirely human concepts only if you've already accepted some different axioms of your own. The Christian argument is that valuing freedom over slavery, and wanting worship, are divine qualities and concepts. And humans share those things because they were made after God's likeness for the sake of being loved (and more importantly, loving God in return).
You care about the things you love. The single "human-like" trait of my reasoning is to be able to love. I do not like the "human-like" term because it involves so many negative connotations. If God is perfect, I can not imagine him as "human-like" ;-).
Human-likeness is not a very popular trait to attribute to a higher power because it shows the underlying anthropomorphism at work.
There is no reason to think that if there is some sort of higher power, it has an any bigger interest in humans than it has with atoms or planets. To assume that is an assumption, which shouldn't be hidden.
The difference between scenarios is that God is God, the one that may have created everything including your cat or at least (the other extreme of God definition for believers) the "thing" that differentiates love from a chemical reaction.
To be honest, we don't know either, so the agnostic viewpoint (compared to atheistic) would be that it is equally valid. Either you believe in random chance or you believe in God.
I'm always perfectly happy when someone calls the big bang the moment of creation. It could have been.
>Either you believe in random chance or you believe in God
Not really true.
"We don't know exactly how the Cambrian explosion came about, but have a lot of good evidence on how evolution works, which allows us to probe deeper into theories about what happened" is not equivalent to "it's all random chance!"
Most religious people (or at least most widespread religions) essentially accept evolution, you know. Hard evolution denialism (especially young earth creationism) is largely peculiar to certain forms of evangelical Protestantism and some factions of Islam, these days.
I do not differentiate between agnostic and atheistic thought. They are both the same thinking/belief systems in my view. An agnostic believes there could be a "god/creator" (but does not pursue this thought any further than "maybe"). An agnostic also believes there may not be a God/Creator given the absence of evidence to justify such a belief. An atheist believes that there is NO god/creator given the absence of evidence to prove the existence of such a being. If evidence had to exist then the atheist will believe the existence of such a being based on such evidence. That sounds exactly the same.
As to your point about "we don't know" - well, not knowing is perfectly fine in science. We cannot ascribe to or embellish and fabricate imagined facts and agents to any unknown phenomenon without evidence.
> I do not differentiate between agnostic and atheistic thought.
I find it very interesting that in de US there seem to be a lot of gnostic atheists (they know for certain there is no god, and are very vocal about this), while in Europe most people would be agnostic atheists, and they don't care as much.
In order to decide whether you believe in something, you have to know what "something" the question is about. The concept of "God" in western society is often so vague it is impossible to have an opinion either way - for some it means "the absolute", for some it means "the force of creation in the universe". I don't think you can meaningfully say you don't believe in such unspecific concepts. But if you go into more concrete religious beliefs, like "God created the world in seven days" or "God punished the wife of Lot by turning her into a pillar of salt" or "Jesus is the only path to God", then it is easier to decide whether or not you actually believe it or not.
My impression is Biblical literalism is more widespread in the US compared to Europe, which in turn is easier to decide for or against. Especially the discussion about evolution vs religion is almost entirely absent in Europe. Framing evolution as opposed to a belief in God means it is pretty easy to become an atheist, since we have overwhelming evidence for evolution.
I always liked the "Radiological explanation" regarding the Cambrian explosion.
Higher-than-normal levels of radiation would provide the mutagenic effects on all life. Many things would die because of dead-end deviations.
I look at the area around Chernobyl at what radiation can do for evolution. Of course, it's pretty terrible for suffering on a whole, but we're talking about evolution. Life gets messy.
Yip. He insists on hammering the vast wonders and myriad colours of life through the same blunt instrumentation of non-sequiturs and other horrendous logical fallacies. He simply cannot accept the removal of a "God's hand" in any conversation of scientific import. Conversations with him can get comical only if you insist on ignoring that he is a medical doctor to boot.
My understanding is that something very much like this is what is theorized to have kicked off a more recent 'explosion', that of angiosperms.
Essentially there was some chromosome doubling which set the stage for the huge diversity and abundance of flowering plants which quickly dominated the planet. In the Wikipedia article on angiosperms it states, "The evolution of seed plants and later angiosperms appears to be the result of two distinct rounds of whole genome duplication events."
I'm sure something like this is one of the more plausible triggers for the Cambrian.
I was thinking - it's not an area I know much about really - but if something like that happened in the Cambrian you could probably figure out what by looking at the DNA of explosion descendents and species that were not involved and seeing what sequences were in the first group but not the second.
- high-altitude adaptations of Andean populations (independent Ethiopian and Tibetan adaptations are older than your 10KY limit)
- possibly HgbS? Couldn't find much numbers related to its evolutionary history. And it's just one of the independent evolutions for malaria resistance: Thalassemias, Duffy blood groups and a few others seem to provide some level of malaria resistance to malaria
- CCR5-Δ32, while it provides resistance to HIV it's too old to have been selected for it but it's too young to have not been selected for as well (95% confidence that it's 900 to 5000 years old, likely circa 2250, a non-selected random survival would be ~100kY given how widespread it is)
And narrowing jaws make us ever more likely to miss some wisdom teeth. They part always struggle to emerge from the gums from narrow jaws due to our large brains, and are also less necessary today with softer foods. Softer foods also weaken our jaw muscles a bit, so they are more likely to remain under the gums and cause infections.
All in all, they are probably more or less going away in the long run.
The timespan of a generation in humans is about 20 years. So in 5000-10000 years that's 250-500 generations, a tiny amount.
For evolution to happen, a genetic mutation has to endow an advantage that makes its carrier more likely to survive and reproduce. Given that the reproductive selection process (which characteristics are attractive to a mate) is largely driven by cultural norms now, it's hard to see what advantages are going to raise a person's chances of reproducing. Fashion tastes change several times in a single generation.
Women are often said to like taller men. Well we are getting taller as a species [1]. If men prefer a woman with a certain 'look', maybe women are evolving towards that look (it seems like a much harder thing to quantify). Manipulative, cheating males have more sexual partners - maybe we're evolving towards more of that kind of behaviour.
If you're expecting humans to grow extra arms or become super-strong or something, I don't think it's going to happen. Extra limbs is too 'abnormal' and culture doesn't like that. Being physically strong doesn't affect chances of survival in humans any more. Same applies to better vision, hearing... any super-senses. They don't affect our survival. I've heard people posit that maybe we'll lose our little fingers as they don't do anything. Same again though - even if it's true that we don't use them, it doesn't mean that someone born without little fingers is going to have a higher chance of reproducing.
Our development happens at a rate much faster than biological evolution now because of culture (meme vs gene). A lot of what constitutes a modern human is external (as a thought experiment just imagine what a human would be like if he'd never spoken to another human, read anything, or absorbed any culture in any other way). From this point of view, cultural evolution could be seen as evolution v2.0 as it happens and spreads much more quickly that genetic evolution.
The interesting question is if human changes are liable to speciate or not.
It is possible that just a few changes would result in biological incompatibilities. Combine it with differentiating sexual selection and things might become interesting.
If humanity in its current state somehow manages not to destroy itself (and much of everything else) the probability of speciation of our survivors is close to a certainty. Not so much as a consequence of natural selection or sexual selection but of human selection.
If we survive another 100 thousand years, we will inevitably see another emergent species genetically superior but incompatible with current homo sapiens. I think that will be an incredible day for humans to acknowledge (the death/extinction of homo sapiens). We had better sort our differences out before that day arrives.
I think it's unlikely these days because we all intermingle too much. If anything it'll go the other way with races fading out as our descendents become mixed.
Yes I am assuming a large and notable mutation. Humans fought for thousands of years with implements so where is the human with Star Trek armor skeleton.
I guess in the books the diversity caused evolution is strong and notable
Ps choosing your mate is a recent thing for humanity
Well humans have evolved and are still evolving, there are differences between humans that emerged in the last few thousand years, or what do you call the differences between the human races.
"There are only a few groups who diverged at a set time and remained discrete until now. The KhoiSan split off from the rest of us 100,000 years ago, and the Australian Aborigines about 40,000 years ago. Native Americans, who are a sub-set of the East Asian population, became isolated from population-exchange with Eurasia and Africa 12,000+ years ago." [1]
The thing is humans in the modern age intermingle much more so the differences are subtle and much harder to pick out since they don't remain as discrete.
- Humans have evolved. Look at our huge array of characteristic physical appearances. These differences have emerged in spite of the fact that we all share an extremely common same-species common ancestor. And that's just what's on the outside. Our primary divergence from our evolutionary (different species) ancestors has not been what's on the outside, as we've become worse in nearly every way, but what's on the inside. Intelligence > all. Discussing this topic as it relates to humans today is very sensitive.
- Evolution is driven by natural selection and ultimately by who's most successful at breeding. Humanity has socially evolved in a bizarre way in that today those who are least successful tend to breed far more successfully than those are more successful. Lower income, lower education, and higher religiosity are strongly correlated with higher fertility.
The Flynn Effect [1] was the observation that 'real' IQ scores were constantly increasing in developed nations. This was a major issue since IQ is normalized such that for any given population that mean is always 100 with a standard deviation of around 15. That means that somebody in 1960 with an IQ of 100 was probably more intelligent than somebody from 1920 with an IQ of 100. This was convenient for the environmental view of intelligence as improvement in environmental factors correlated with the increases in IQ. However, the Flynn effect in many developed nations has actually reversed, in spite of the continuing improvement in environmental factors. It continues to remain in effect in less developed nations. There are many ways to interpret this, but it's certainly interesting to consider it from an evolutionary perspective.
By evolution, we assume you mean "turn into another species". If so ...
But then neither has the mosquito "evolved", or the shark. At a genetic level changes are continuous in every organism and genetic changes can even happen as rapidly as from one generation to next. We may not see the molecular changes translate to the phenotype level but the changes are there. (See topic of epigenetics)
Actually, you can see changes at phenotype level too (e.g body morphology of offspring affected by the diet of parents).
Other theories: The sun calmed down enough so that large large organisms be near the light without being zapped with radiation, the algeal mat that covered the ocean got eaten by animals and this opened the possibility of ecosystems, the earth unfroze, the chemistry of the oceans changed.
I feel like at this point it’s not too far-fetched to say with absolute certainty that earth is in the process of a long-term terraform by some alien species, and that humans represent the final step of that process, by warming the earth and making sure carbon is properly distributed through the atmosphere, as well as collecting and separating the metals that our alien overlords will feast on. When they’re done feasting on us.
The major problem—one of the major problems, for there are several—one of the many major problems with the panspermia argument is that space is a very unfriendly place for anything living to reside. Okay, it might be that conditions on Earth were harsh at times, but that by far doesn't seem to match those found in space. At geological time scales, space just doesn't appear very safe for life.
Not saying that I support this, but it gives an interesting touch to the creation of Adam in the Bible.
In Genesis 2,7 it says:"Then the Lord God formed a man from the dust of the ground and breathed into his nostrils the breath of life, and the man became a living being." [1]
In the abstract of the paper it says "living organisms such as space-resistant and space-hardy bacteria, viruses, more complex eukaryotic cells, fertilised ova and seeds have been continuously delivered ever since to Earth".
Besides from skipping lots of evolutionary steps, if those organisms have been delivered to earth by some cosmic object (a hand of God?), then man ultimately formed from that dust.
I am by no means religious, but it's an interesting thought experiment.
Is composed of hydrogen, oxygen, nitrogen, carbon and phosporus. 4 out of 5 elements there are guaranteed, certified remains of one ancient star or another.
Or. Like Carl Sagan said, "We are made of star stuff".
Uhm no, it is not exactly what you said. You exactly wrote:
"...but it's an interesting thought experiment".
Your story is not a thought experiment of any kind. It's just an unstructured, unverifiable, lacking in continuity idea. It just a "thought" on its own.
https://news.ycombinator.com/item?id=17110874 (82 points/123 comments)