When Darwinians labor to reconstruct human evolution, they usually rely on the fossil record and comparative antomy. Of course, there's a circularity to that procedure. You must assume that certain fossils are related to humans in the first place. But let's bracket that for now.
What can we infer about humans or our alleged evolutionary ancestors from anatomy?
i) Eye-placement. Why do some animals have forward-facing eyes while other animals have eyes on the sides of their heads?
The conventional answer is that predators need binocular vision. That gives them depth perception, which they need to perceive prey at a distance, detect camouflaged prey, and chase it. By contrast, prey species need peripheral vision to detect predators that are sneaking up on them.
And, in general, that's probably a good explanation. But how does that explain human eye-placement? Humans aren't natural predators, in the sense that we don't have the standard equipment to be predators. We lack fangs, claws, speed, strength, or venom.
Moreover, according to evolutionary theory, we're not descended from predators.
We became predators because we had the intelligence and dexterity to design and operate weapons–and not because nature designed us to be predatory. Likewise, we domesticated certain animals (dogs, horses) to aid us in hunting. None of that's inferable from human anatomy.
A fallback explanation is that humans are descended from arboreal animals. Our ancestors needed binocular vision to judge depth in jumping from branch to branch. There are, however, some problems with that explanation:
a) Squirrels have eyes on the side of the head.
b) Once we came down from the trees, our eye-placement became disadvantageous rather than advantageous. At that stage of human evolution we were essentially prey species. Extremely vulnerable to land predators.
So why didn't our eyes migrate to the sides of our heads the way the eyes of flatfish migrate to one side, as an adaptation to new conditions?
ii) Humans lack the dental equipment of predators like wolves and leopards. Yet humans enjoy a meat diet when that's available. For that matter, humans eat i pizza, ice cream, chocolate bars. You could never infer human diet from human teeth. Even if we had the teeth of wolves and leopards, we'd still eat pizza, ice cream, chocolate bars. Our dietary behavior isn't inferable from our dental equipment. We eat whatever we like.
iii) Consider a related example. Many human adults drink milk. Not just babies. Now, one might infer that human adults drink milk because we have the lactase enzyme. But isn't it the other way around? We have the lactase enzyme because we drink milk.
The availability of milk is based on domesticating cows and goats. And lactase is an adaptation to a milk diet. For instance, Asians are more prone to lactose intolerance than Caucasians.
So that's a case where you can't infer behavior from biology, inasmuch as the behavior is driving the biology, rather than vice versa.
iv) You'd never know from examining the human face that kissing is a major form of foreplay. That's because the placement of the nose (especially the aquiline Caucasian nose) gets in the way of kissing. Yet we manage to around it.
Squirrels lack reversible thumbs too. So what? Squirrels' adaption to the trees is not the same as apes. Would you suggest reversible thumbs in apes is superfluous?
ReplyDeleteEye placement in humans is disadvantageous to humans in so far as being prey, but is advantageous in other ways, whether it be being a predator, foraging for food, and so on. Even if it would be more advantageous for eyes to move to the side of the head, not every advantageous change is guaranteed to occur in evolution.
Human adaption to eating meat may well coincide with use of tools (spears), which is why carnivorous teeth was an unnecessary evolutionary step.
Not sure of your milk question. Some humans in the past gained an evolutionary advantage in being able to digest milk, and that trait spread widely.
I don't have any problem kissing. A pity you do :D
@ccthecc
ReplyDelete"Squirrels lack reversible thumbs too. So what? Squirrels' adaption to the trees is not the same as apes. Would you suggest reversible thumbs in apes is superfluous?"
Do you mean opposable thumbs? Otherwise you just sound ignorant.
Do you mean adaptation? Otherwise you just sound ignorant - again.
"Eye placement in humans is disadvantageous to humans in so far as being prey, but is advantageous in other ways, whether it be being a predator, foraging for food, and so on. Even if it would be more advantageous for eyes to move to the side of the head, not every advantageous change is guaranteed to occur in evolution."
You're tilting at windmills. None of this contradicts Steve Hays' post which is about what's inferable (or not) from human anatomy from modern evolutionary theory.
"Human adaption to eating meat may well coincide with use of tools (spears), which is why carnivorous teeth was an unnecessary evolutionary step."
This is the second time you've evidently incorrectly used "adaption" rather than "adaptation" when "adaptation" would presumably be in view. This is a reflection you're not familiar with the terminology, and thus you're probably not well read on the topic at hand - i.e. neo-Darwinism.
More to the point, where's your evidence "Human adaption [sic] to eating meat may well coincide with use of tools (spears)"? For example, elephants can use tools. But do elephants normally eat red meat? What's the differential factor(s) between humans vs. elephants in this regard?
What exactly are you referring to when you say "carnivorous teeth"? Let's briefly compare the crowns of different types of human teeth. The crowns of premolars are bicuspid. The upper molars have four cusps on their crowns, while the lower molars have five cusps on their crowns. The crowns of incisors are chisel-shaped by which I mean upper and lower incisor crowns don't meet edge to edge, but instead by a sliding overlap like we see in scissor blades. By contrast, the crowns of canines are pyramidal or conical. So which of these would you infer are "carnivorous teeth" based on their crowns?
Related, given modern evolutionary theory with "evolutionary step[s]," how could these types of teeth have evolved independently of one another?
(And all this doesn't even consider other aspects of dentition such as enamel, roots, nerve supply. Or the eruption and replacement of deciduous teeth as infants mature to adults.)
Let's hope you haven't bit off more than you can chew here! :-)
"Not sure of your milk question."
DeleteTo be fair, I'm not sure of most of what you've said here. It all might as well be non sequitur after non sequitur.
"Some humans in the past gained an evolutionary advantage in being able to digest milk, and that trait spread widely."
Of course, many if not most of those who question macroevolution would not have a problem accepting microevolution.
Perhaps a more pertinent question is the entire framework or meshwork on which lactose digestion and lactase enzyme activity depend. How could the framework itself have evolved all at once to produce these effects and so on? For lactose intolerance is the inability to digest lactose (i.e. milk sugar). It's caused by insufficient lactase (i.e. an enzyme) activity. Normally, the lactase enzyme converts lactose into glucose and galactose. But without sufficient lactase activity, lactose can't be converted, and thus can't be absorbed into our bodies. Instead, it remains osmotically active. This in turn can cause water retention in the gastrointestinal tract as well as production of a watery diarrhea. What's more, bacterial degradation of lactose produces lactic acid and hydrogen gas, which then can cause abdominal bloating, flatulence, and cramps. And the pH of stool is acidic.
In other words, given modern evolutionary theory, what would be the "evolutionary step[s]" necessary to evolve such a delicately balanced biochemical system in the first place? One could perhaps see evolution occurring after the system is already in place, but one would be hard-pressed to see it occurring before. Yes, once the system is in place, then (micro)evolutionary refinements could occur. But how does the system itself first come into play?
"I don't have any problem kissing. A pity you do :D"
Sure about that? One could easily doubt those you've (allegedly) kissed would say the same about you. :-)
Adaption and adaptation are similar, but subtly different words that are both used about evolution. If you want to google it you'll find thousands of references. Like this one: http://www.amazon.co.uk/Evolution-Threshold-Adaption-Secondarily-Vertebrates/dp/0520252780
ReplyDeleteI realise of course your modus operandi is to argue around the periphery when you have nothing of substance to say about the main argument, but its sad to see you so transparently resorting to ad hominem that allegedly I don't know what terminology is correct, thus leaving you to attack the messenger rather than the message.
The difference between Elephants and humans, is that humans use tools to hunt and elephants don't. If you use tools to hunt you don't need to evolve teeth to do it for you.
Which teeth are carnivorous? I don't care. The allegation is that human teeth are not carnivorous, humans eat meat, therefore evolution is not true. That's a ridiculous argument.
I don't understand why you think different types of teeth would not be able to evolve "independently". You'd have to do a lot better at putting together a cogent argument on that for any evolutionary scientist to take your point seriously.
You struggle to accept that humans could have adapted to milk. And yet even a creationist can't seriously dispute that even in our own lifetimes, scientists have invented various new and novel herbicides such as glyphosate, and over a relatively short time period weeds have adapted to the new herbicide and spread throughout the country to the point that it may well be now useless to use that herbicide. And that's happened within human memory, and we don't need to contemplate some complicated series of steps for it, it just happened. The same thing happens for bacteria and antibiotics and so forth.
I would also point out that there is lactose in the milk of all mammals, including humans. Since by definition, all mammals feed on milk, it's hardly a jump of wonder for a mammal to be able to adapt to milk products. That you would suggest it as your Coup de Grâce, is a bit ridiculous really.
@ccthecc
Delete"Adaption and adaptation are similar, but subtly different words that are both used about evolution."
Your usage isn't salvaged by the distinction since you weren't using the term in a "subtly different" way at all.
"If you want to google it you'll find thousands of references. Like this one: http://www.amazon.co.uk/Evolution-Threshold-Adaption-Secondarily-Vertebrates/dp/0520252780"
This is just your ex post facto attempt to justify your original lack of familiarity with evolutionary terminology.
"I realise of course your modus operandi is to argue around the periphery when you have nothing of substance to say about the main argument"
You didn't actually have a "main argument" to refute.
"but its sad to see you so transparently resorting to ad hominem"
But when you "resort to ad hominem," you get a free pass?
"that allegedly I don't know what terminology is correct, thus leaving you to attack the messenger rather than the message."
You mixed up "reversible thumbs" for opposable thumbs. That's a pretty big blunder on your part.
"If you use tools to hunt you don't need to evolve teeth to do it for you."
This is dumb:
1. For one thing, even on evolutionary grounds, what makes you think "using tools" and "evolving teeth" are mutually exclusive, such that if an animal uses the former, it doesn't need the latter?
2. Also, I guess so much for human incisors which (as even evolutionists will tell you) are normally used for biting and cutting, and canines for holding and tearing!
3. By your logic, if you use tools to drink water, then you don't need to evolve mouths to do it for you.
4. Do you think whichever hominid (or pre-hominid) modern humans supposedly evolved from would have had to rely mainly on, say, their teeth to hunt until they somehow could make tools? What did they do to survive in the interim, as this evolutionary transition was occurring? Was there ever a point when hominid teeth were like, say, saber-toothed tiger teeth in your view?
5. Also, it wouldn't necessarily only involve the teeth. Take how much force a crocodile can slam their jaws shut with. Could pre-tool-making hominids ever do something like this?
"Which teeth are carnivorous? I don't care."
You brought it up.
"The allegation is that human teeth are not carnivorous, humans eat meat, therefore evolution is not true. That's a ridiculous argument."
What's "ridiculous" is your failing to understand Steve Hays' argument.
"I don't understand why you think different types of teeth would not be able to evolve 'independently'."
For example, check out the entire field of systems biology.
"You'd have to do a lot better at putting together a cogent argument on that for any evolutionary scientist to take your point seriously."
No, I don't, since you're obviously not an evolutionary scientist. Rather, I just need to say enough to undermine what you've said, which is what I've done. Anything else is gravy.
"You struggle to accept that humans could have adapted to milk."
Not if you read what I actually wrote.
"And yet even a creationist can't seriously dispute that even in our own lifetimes, scientists have invented various new and novel herbicides such as glyphosate, and over a relatively short time period weeds have adapted to the new herbicide and spread throughout the country to the point that it may well be now useless to use that herbicide. And that's happened within human memory, and we don't need to contemplate some complicated series of steps for it, it just happened. The same thing happens for bacteria and antibiotics and so forth."
DeleteOn the one hand, you don't bother to show how these are analogous. You're just asserting they're analogous without benefit of argument.
On the other hand, I actually have no problem with anything you've said here. It certainly doesn't undermine anything I've said. What's more, in fact, I actually pointed this out in my previous comment to you, which you evidently missed. (You seem to have difficulty with reading comprehension.)
"I would also point out that there is lactose in the milk of all mammals, including humans. Since by definition, all mammals feed on milk, it's hardly a jump of wonder for a mammal to be able to adapt to milk products."
Among other issues, you're falsely assuming adaptation is identical to the evolution of body plans.
"That you would suggest it as your Coup de Grâce, is a bit ridiculous really."
No, I never suggested this was my coup de grâce. I never had such delusions of grandeur. Rather, as I've said, I just need enough to successfully argue against your point (such as it is), which again is what I've done.
ccthecc
Delete"Squirrels lack reversible thumbs too. So what?"
Logic is not your forte. If an evolutionary biologist says humans have forward-facing eyes because our arboreal ancestors had forward-facing eyes because they needed that eye-placement to accurately leap from branch to branch, and I cite an obvious counterexample, then that invalidates the inference.
"Would you suggest reversible thumbs in apes is superfluous?"
i) I assume you mean "opposable," not "reversible."
ii) Since most animals lack opposable thumbs, there's an obvious sense in which they are superfluous. Useful, but unnecessary in most cases.
iii) Anyway, your question is uncomprehending. It's an issue of whether evolutionary reasoning is consistent or arbitrary.
"but is advantageous in other ways, whether it be being a predator, foraging for food, and so on."
Since both predators and herbivores forage for food, even though they typically have different eye-placements, how is that advantageous for both?
"Even if it would be more advantageous for eyes to move to the side of the head, not every advantageous change is guaranteed to occur in evolution."
i) So how did early man survive?
ii) Moreover, your excuse illustrates how evolution is practically unfalsifiable. If an adaptation confers a survival advantage, Darwinians says that's evidence for evolution, If, however, there is no beneficial adaptation, that doesn't count as evidence against evolution. Heads I win, tails you lose.
"Human adaption to eating meat may well coincide with use of tools (spears)…"
One needn't be a hunter to be a meat-eater. Take farmers and ranchers who domesticate animals (e.g. chickens, cattle, pigs) for food.
"which is why carnivorous teeth was an unnecessary evolutionary step."
Irrelevant. The question at issue is whether we could infer human diet and corresponding behavior from human dental equipment.
"Not sure of your milk question."
Another example of your logic-challenged understanding. As I explicitly stated, the question is the direction of inherence. Do human adults drink milk because we have the relevant enzyme, or do we have the relevant enzyme because we drink milk?
"Some humans in the past gained an evolutionary advantage in being able to digest milk, and that trait spread widely."
i) How do you know that? What's your evidence for that prehistoric narrative?
ii) What makes you assume human adults drink milk because that's advantageous rather than enjoyable? Do humans consume candy and pastries because that's advantageous?
"The allegation is that human teeth are not carnivorous, humans eat meat, therefore evolution is not true. That's a ridiculous argument."
You're terribly dense. The argument concerned the limitations of inference.
"I would also point out that there is lactose in the milk of all mammals, including humans. Since by definition, all mammals feed on milk, it's hardly a jump of wonder for a mammal to be able to adapt to milk products."
Another example of your chronic incomprehension. The question at issue was adult milk consumption.
I don't have time to waste on captious, obtuse commenters. You lack adaptive intelligence. Unless you can evolve to a higher plane of reasoning, further comments will be deleted.
@ccthecc
Delete"Some humans in the past gained an evolutionary advantage in being able to digest milk..."
Most of the world's adult population (with a few exceptions like Northern Europeans and some Africans) actually doesn't need milk (or other dairy products) to survive. At least if we consider the fact that most of the world's adult population is lactose intolerant (to varying degrees) but does just fine health-wise.
Milk is something like 85% water, 5% fat, 5% sugar (lactose), and the rest mainly proteins and vitamins and a few miscellaneous products. We can good substitutes for all of these from other sources besides milk.
"scientists have invented various new and novel herbicides such as glyphosate, and over a relatively short time period weeds have adapted to the new herbicide and spread throughout the country to the point that it may well be now useless to use that herbicide. And that's happened within human memory, and we don't need to contemplate some complicated series of steps for it, it just happened. The same thing happens for bacteria and antibiotics and so forth."
As far as herbicides and antibiotics:
1. You're sloppily attempting to argue weeds or bacteria acquiring resistance to herbicides or antibiotics is evidence for evolution. The simple answer is what you consider "evolution" here could be chalked up to microevolution rather than macroevolution (which is what I said earlier).
2. Related, it's one thing to say weeds or bacteria acquiring resistance to herbicides or antibiotics involves minor genetic modifications in pre-existing molecules. But it's quite another to say weeds or bacteria acquiring resistance to herbicides or antibiotics involves the evolution of entire enzymes or other molecules let alone the de novo formation of entire enzymes or other molecules.
3. Also, many weeds and bacteria acquire resistance to herbicides and antibiotics at the cost of deleterious mutations to themselves (rather than beneficial mutations). It's sort of a Pyrrhic victory in that the weeds or bacteria can continue to survive against the herbicide or antibiotic, but at the cost of hampering part(s) of their genome. I'll simplify, but it's akin to how some people who live in swampy regions with lots of malaria-carrying mosquitoes have developed the gene for sickle-cell disease. On the one hand, having sickle-cell disease protects people from getting malaria since it's harder for the malaria virus to survive in a sickle-cell shaped red blood cell than in a normal red blood cell. But on the other hand, having sickle-cell disease (anemia) can lead to significant health problems and even death for the person.
The real weakness of evolution, in my opinion, is it's adaptability to any set of data with a just-so story. There are just-so stories to explain heterosexuality, but then just-so stories to explain homosexuality and every other type of sexuality. These stories are then touted as instances of how "nothing makes sense without evolution." You can imagine a just-so story about why an animal has that sort of teeth and then when it's pointed out relevantly similar types of animals don't have that teeth all you need to do is imagine a just-so story about why that is. Of course you never need to provide evidence for the imagined story itself. Once you've imagined the story then the story itself is the validation of evolution and its indispensability.
ReplyDeleteMany things seems to me to make unguided macroevolution improbable. Two examples (of many) would be instinct in animals and reflexes.
ReplyDeleteHere's a link to a Wiki article on Reflexes
Reflexes often require the coordination of different bodily systems. It's difficult to imagine how they could have evolved such coordination. Why, for example, do you automatically close your eyes when sneezing? It's nearly impossible to keep your eyes open when you sneeze. Well, if you've ever sneezed facing the ground you'd realize how the automatic closing of your eyes helps keep much of the dust you've propelled off the ground out of your eyes.
Various bodily functions have multiple functions. For example, breathing and sneezing actually help lymphatic fluid to flow. So, sneezing not only expels irritants out of the respiratory system, it actually also helps better fight infection because the white blood cells flow faster/freer in the lymphatic system. Breathing slowly and deeply builds pressure in the digestive system to aid in defecation.
How did the flinch response evolve? As far as I know eyelids aren't connected to eyes directly in the nervous system. They're connected via the brain.
Gag reflex
http://www.reasons.org/articles/its-no-gag-pharyngeal-reflex-shows-intelligent-creation
Infant reflexes during childbirth
http://www.discovercreation.org/documents/InfantReflexesEvolvedorDesigned.htm
How did the ejaculatory reflex evolve? Without it reproduction of certain species wouldn't be possible.
Regarding instincts, there are various kinds. One of many would be migration. It's amazing how birds, fish, butterflies and other animals migrate. How do they know when they've arrived and it's time to spawn? Certain fish migrate hundreds of miles and spawn in the vary locations they themselves were hatched. Why do multiple generations of butterflies live and die on their way to a destination only to return to again to where they started (again through multiple generations)?
How do birds know to overeat when the food supply is the highest in order to have the fat reserves to reach their destination when they migrate for winter? How do they know winter is coming? How do birds fly vast distances over water not knowing they'll have enough strength to reach land? If they attempted it the first time without sufficient fat and without knowing the best route to their destination they'd die of exhaustion and fall into the ocean that first generation. Then they wouldn't have survived as a species or subspecies.
How did animals evolve to use the stars, or the magnetic poles or the magnetic minerals in mountains to help them navigate their way to their destinations when migrating?
How did dogs evolve the instinct to paddle when entering water? There are a lot of funny youtube videos on this (e.g. here or here et cetera).
These are just some curious things I wonder about.
I admit there may be evolutionary theories that can answer some or all the questions I've asked since I've asked them as someone mostly ignorant of evolutionary theories.
Apparently, some herbivores (like deer) sometimes resort to eating meat. Probably to supplement an inadequate diet.
ReplyDeletehttp://news.nationalgeographic.com/news/2003/08/0825_030825_carnivorousdeer.html
http://www.npwrc.usgs.gov/news/press/ontape.htm
http://io9.com/field-cameras-catch-deer-eating-birds-wait-why-do-deer-1689440870