- Life is robust
- Ghosts of evolution
- Warm and cold blooded
- Behaviour and genes
- Evolution of plants
- Evolution of organs
- Most evolution is one species slowly becoming another
- Respiration limits size
- Life is more than a generation
- Nature is a lazy engineer
Nothing in biology makes sense except in the light of evolution.
- Theodosius Dobzhansky, the title of his 1973 essay.
Evolution could so easily be disproved if just a single fossil turned up in the wrong date order. Evolution has passed this test with flying colours.
- Richard Dawkins, The Greatest Show on Earth: The Evidence for Evolution
Seen in the light of evolution, biology is, perhaps, intellectually the most satisfying and inspiring science. Without that light it becomes a pile of sundry facts - some of them interesting or curious but making no meaningful picture as a whole.
- Theodosius Dobzhansky
Adapt or perish, now as ever, is nature's inexorable imperative.
- H. G. Wells
We are essentially elaborate replicative systems that have evolved into codependent niches.
Fish did most of the work. They developed digestive systems, muscles, eyes, and brains. All of the complexity of animals have built upon their work.
The physical appearance of a plant or animal is the physical expression of its genes, as doctored by its environment (and its age)
Particularly in epochs of change, beauty is not the greatest genetic guarantee. Adaptability and intelligence are.
Evolution is a truly vast topic.
Natural selection simulation
Life is robust
Life has been through a hell of a lot, and it has innovated its way through problems so diverse that our small ability to understand cannot comprehend it.
The only thing that may sterilise this planet is the Suns expansion. Or perhaps some kind of intense solar radiation or sustained bombardment.
However, there is no guarantee that civilisation, beauty, or intelligence will survive such events.
Ghosts of evolution
Evolution leaves ghosts everywhere.
In continent_, the avocado evolved alongside a kind of megafauna called __. Only this animal was large enough to eat an avocado, seed and all.
The animal would disperse the seed in its poo, and the avocado plant would grow in a new area.
When human beings arrived in _continent_, we inadvertently send megafauna_ extinct, but we also discovered the avocado and eventually exported it all over the world.
But it still carries its large seed, the remanent of its relationship with a species long extinct, like a ghost in its genes.
Warm and cold blooded
Robert Bakker, Reddit AMA
Matthew T. Mossbrucker, Reddit AMA
Avoid the false binary of "warm-blood" versus "cold-blood" when thinking of dinosaurs. Body chemistry is a spectrum.
All dinosaurs put together show a range of endothermy like you see today in all birds. Kiwis are less endothermic than parrots. But they're still endothermic.
Earliest hint of endothermy is middle permian, South Africa. The butt headed mammal like reptiles.
Wikipedia, The Dinosaur Heresies
The book sums up the extant evidence which indicates that dinosaurs, rather than being cold-blooded and wholly lizard-like, were in fact warm-blooded, agile creatures more similar to modern birds than to lizards or other reptiles. Although controversial on publication in 1986, the passage of time has proven Bakker correct in many respects, and much of *Dinosaur Heresies* now represents the prevalent view in paleontological circles (although other parts have been outdated by more current research).[*citation needed*]
The main arguments used to show that dinosaurs were warm blooded are:
Almost all animals that walk upright today are warm-blooded, and dinosaurs walked upright.
The hearts of warm-blooded animals can pump much more effectively than the hearts of cold-blooded animals. Therefore, the giant *Brachiosaurus* must have had the type of hearts associated with warm-blooded animals, in order to pump blood all the way up to its head.
Dinosaurs such as *Deinonychus* led a very active life, which is much more compatible with a warm-blooded animal.
Some dinosaurs lived in northern latitudes where it would be impossible for cold-blooded dinosaurs to keep warm.
The predator/prey ratio of predatory dinosaurs to their prey is a signature trait of warm-blooded predators rather than cold-blooded ones.
Birds are warm-blooded. Birds evolved from dinosaurs, therefore a change to a warm-blooded metabolism must have taken place at some point; there is far more change between dinosaurs and their ancestors, the archosaurs, than between dinosaurs and birds.
Warm-blooded metabolisms are evolutionary advantages for top predators and large herbivores; if the dinosaurs had not been warm-blooded there should be fossil evidence showing mammals evolving to fill these ecological niches. No such evidence exists; in fact mammals by the end of the Cretaceous had become smaller and smaller from their mammal-like-reptile ancestors.
Dinosaurs grew rapidly, evidence for which can be found by observing cross-sections of their bones.
Behaviour and genes
- Plants can only progress through slow genetic changes and lucky dispersion. (Bear in mind that from the plant's perspective they don't know why doing things like producing sweet sticky nectar results in fertilisation, it just happens. It just sees that it's pollen gets dispersed, so it got better at it. We have studied this and know that animals and insects feed on the nectar and pollenate, but the plant doesn't even know why it works. But this can be continued. It doesn't even know what fertilisation is, it's body just creates the apparatus to make it happen because its genes instruct it to do so. It is blind and dumb, and can know only its own body plus a few external forces like sunlight.
- But plants can also be successful through responding to their environments. It turns out that plants are actually very attuned to stimuli like light and touch. Cues from these senses initiate responses, presumably predetermined at a genetic level. Again it doesn't know why it does so, it is just programmed by its genes.
- Animals take it a step further in that they can make their own decisions to supplement genetic responses. Usually these decisions are based on past experiences.
- Behaviour is guided to success by the brain through what we call " feelings". These feelings as guides to actions are usually determined genetically, and so genes that encourage actions that encourage the genes being spread become more prevalent. This means that necessities of life for animals like eating food are rewarded and so is sex and looking after your baby.
- However the brain, which organises all this, is very complicated and not everything lines up perfectly.
- Animals don't know what the true purpose of many of their actions are, they are just motivated by a secondary effect of their actions, being a reward or punishment from their brain.
- Some animals with larger brains can actively problem solve in order to gain this good feeling or avoid a bad one. Crows and chimps are a few animals that can purposefully perform a series of actions together to get what they want, demonstrating the ability to reason.
- Humans take it to a whole new level. Hunting techniques, social structures, tools, language, fire, farming, buildings, weapons, strategy, and law was the bedrock that civilisations are built on.
- Every now and then people turn their capacities towards less practical but more universal questions about the nature of man, life, and the universe. We call the process science and philosophy, and often, especially in science, it turns out that these have yielded many very practical results.
- Incidentally we've discovered along the way the true purpose of many of the actions of ourselves and of animals. We know why we have to eat, why we have sex, and to a large extent have worked out the role that genes play in encouraging this behaviour.
- But we are still very strongly motivated by feeling rather than reason, which is not always a bad thing. Almost always we use a mix of feeling and reason in our judgements, with mixed results. Gut instinct can inform our judgements, as can emotion, or it can cloud it.
- Often we use half-reason, where unexamined beliefs and prejudices are supported by circumstantial evidence and semi logical reasoning. For instance, very often people make judgments without considering a satisfactory amount of the available information before judgment.
- It seems to me that we will have a revolution should education teach skepticism, and the scientific method as a way of obtaining truth, not just a process for scientists.
- At the same time, we should be teaching students about the universe with a strong eye for context and how what we've learnt fits together, and where the limits of our understanding lie.
- Genetics kind of pass on personality.. Think of your own family. You're a little bit like nan, but not too much.
Evolution of plants
Includes the beginnings of different modes of insect herbivory (insects eating plants)
- Trees must adapt much slower due to their long lifespans. Especially those in deep forests. Organisms that have a shorter lifespan must have a much faster 'refresh rate' to adaption. Trees may have gone unchanged throughout numerous evolutionary changes or new species in animals.
- Trees are fractal as there is often a pattern of growth that is written into their genes that repeats the same unit.
- Trees and plants create niches, since they create both food and shelter, and other kinds of relationships which are often mutually beneficial.
- Perhaps the same trees and plants have had that same relationship with a number of animal species that have replaced one another over millenia in that particular niche (*if animals evolve faster than trees)* through invasion, extinction, etc.
Its somehow be able to survive, or die for most of them. And quite a lot of pressure comes from other animals. The rest is from the environment. They all react to each other.
But there are long periods of equilibrium.
- Major evolutionary steps, like the evolution of new classes like mammals, reptiles, and birds, must come out of some dramatic disruption of equilibrium.
- Perhaps an extinction event. A very low percentage slice of the population lives and reproduces, and fans out to populate the entire rest of the world. The offspring inherit characteristics of the survivors, explloit the new environment and run into the [[bounds of food and predation]] but eventually diversify into their own niches as the ecosystem re-stabilises.
- There are also events like continental drift (or humans) creating contact between long-separated species. In this case you have invasive species outcompeting natives. In our time, we call them pests or weeds.
- Regular times must be periods of equilibrium - [[most evolution is a species slowly becoming another]]
- The invasive species that are moving in with our human extinction event are the ones that are going to own the future. They are creating massive slices in the total genome for themselves.
- It would be amazing if you could visualise all of the species DNA in a particular environment, and then visualising how it would change – like if an invasive species came in it would multiply and slowly drive out the other species from the total.
- Because generally what happens is one species pushes another out of its niche when it arrives. The size of the DNA pool is practically finite. Very rarely do new niches open up. Climate change or other environmental change can close up niches and open others, however.
- Think of those DNA strands, which run against each other in the replicator genes they have created, with a bit of fuzz in the present as genes are mixed up in crossing over and sex.
- Then think about how each species alive today has likely clawed many series of competitors out of similar niches. How have they done that? By having an adaption.
- Like the first birds that could jump around the legs of the big flying dinosaurs, and probably steal their kills. The number of pest- birds would have multiplied and exploited the meat around the slow pertosaurs until some birds start to change their behaviour and fill different niches, then the pertosaurs dies out because every time it makes a kill it's practically stolen from under it, and then the original species does out because it can't feed that way anymore, but the variants are up and away. That's how a new variation happens.
Evolution of organs
- Sensory organs are the feedback loops of organisms. This includes both negative and positive feedback.
- The brain recognises patterns in those loops.
Most evolution is one species slowly becoming another
Robert Bakker, Reddit AMA
Slow continuous evolution from one daughter species into another is most common among the biggest land herbivores and carnivores. So, we'd expect this kind of evolution among Jurassic stego's and sauropods. In contrast, evolution among raptors should be much bushier and confusing.
Respiration limits size
- Robert Bakker, Reddit AMA
- Meganeura is a giant dragonfly from the late Coal Age. There's a similar guy from the Permian. There is also a gigantic millipede like thing 6-7 feet long, a yard wide. These arthropods are breathing air less efficiently than vertebrates do. So arthropods are more dependent on high oxygen. Dinosaurs and birds have a different way of breathing which is much more efficient than what mammals and gators do. Theoritically the upper limit of a dino / bird system is much higher. That's why you have some of these Argentinian giants.
Life is more than a generation
Although the genes of the parents are mixed up.
Reddit community, We are all one
Nature is a lazy engineer
- Nature is a lazy, sloppy engineer who doesn't care a whit about clean design, but instead is rabidly, single-mindedly focused on *getting the job done* — wherever or however it needs to happen.
- From <https://meltingasphalt.com/border-stories/>