evolution: hard to fathom instances

[0.0]

This is not a religious discussion nor a discussion on whether or not evolution is real. This discussion assumes evolution is real.

What plants or animals seem almost impossible to have evolved? Some instances of evolution can be pretty obvious, like say a giraffe grew a long neck due to the hard to get vegetation that was left by short plant eating animals, or a tiger has stripes because it is harder to see in the grass by its prey.

But what about the really hard to fathom ones?

What about the venus fly trap? How does a plant that sucks up minerals from the soil and gets energy from the sun one day eat a fly and take its nutrients? How does that one get explained by evolution? I mean wow, what a jump. How did this line of nutrition taking even get started? Wouldn't it have to have been fully developed suddenly one day for it to start helping the plant thus helping it down the road of survival of the fittest? What possibly would have been the mechanism? A mutation that suddenly granted a plant this ability in one step has a probability of near zero. What steps led to the venus fly trap? Even with millions of years for this to happen, how does it?

Can you name some hard to fathom evolutionary instances?

[jimrandomh]

The Venus fly trap isn't that hard to explain, actually, if you don't assume that the jump happened in one step. Start with a plant which is commonly eaten by insects. The first mutation causes it to excrete insecticide. Plants with this mutation then commonly have insect carcasses on top of them, and they already have a mechanism which lets them excrete at least one interesting chemical. The next mutation causes them to also excrete a chemical which partially metabolizes the insects to extract some key nutrient. From there, simple mutations (single proteins) can make the plant sticky, make it smell good to insects, and make it metabolize them more thoroughly.

[hipp5]

What plants or animals seem almost impossible to have evolved? Some instances of evolution can be pretty obvious, like say a giraffe grew a long neck due to the hard to get vegetation

Actually, you gotta be careful - something that seems obvious isn't always true. It's now thought that the giraffe's long neck is a result of male giraffes using their heads as weapons when competing for mates. I guess longer necks allows you to hit with more force? I'm sorry for the lack of source on this - it's from my ecology class.

What about the venus fly trap? How does a plant that sucks up minerals from the soil and gets energy from the sun one day eat a fly and take its nutrients? How does that one get explained by evolution? I mean wow, what a jump. How did this line of nutrition taking even get started? Wouldn't it have to have been fully developed suddenly one day for it to start helping the plant thus helping it down the road of survival of the fittest? What possibly would have been the mechanism? A mutation that suddenly granted a plant this ability in one step has a probability of near zero. What steps led to the venus fly trap? Even with millions of years for this to happen, how does it?

Well venus fly traps and other animal-eating plants are generally found in areas of poor nutrition. My guess is that it probably started out as one single mutation that made nectar acidic or something and allowed bugs that fell into its flowers be digested. The extra nutrients from the insects would give an advantage in nutrient-poor environments. From there it was the evolution of structures that made it more efficient.

Hmmmm now I know I've definitely had examples of ones that seemed like an amazing jump to me. Once I remember them I'll post them

[telcontar42]

The wikipedia article on carnivorous plants, http://en.wikipedia.org/wiki/Carnivorous_plant, has some explanation of the evolution of the venus fly trap and similar plants. From reading it, it seems to me like it started with plants with sticky leaves. Insects would get stuck on the leaves and die and the leaves developed a way to absorb the nutrients. The snapping evolved from there as a more effective way for flies to be caught.

One example of evolution that I find pretty amazing is mitochondria. They are thought to have originated as separate organisms in a symbiotic relationship with cells. They were able to produce energy more efficiently so eventually they were hijacked as the method of energy production and became part of our cells. What I really don't understand is how they could have become integrated into our reproduction.

[0.0]

I see my fly trap example wasn't as tough as I had thought. How about this one:

Plants and insects represent a classic case of coevolution—one that is often, but not always, mutualistic. Many plants and their pollinators are so reliant on one another and their relationships are so exclusive that biologists have good reason to think that the “match” between the two is the result of a coevolutionary process.

But we can see exclusive “matches” between plants and insects even when pollination is not involved. Some Central American Acacia species have hollow thorns and pores at the bases of their leaves that secrete nectar (see image at right). These hollow thorns are the exclusive nest-site of some species of ant that drink the nectar. But the ants are not just taking advantage of the plant—they also defend their acacia plant against herbivores.

This system is probably the product of coevolution: the plants would not have evolved hollow thorns or nectar pores unless their evolution had been affected by the ants, and the ants would not have evolved herbivore defense behaviors unless their evolution had been affected by the plants.

The reason given at the end seems circular. http://evolution.berkeley.edu/evosite/e ... tion.shtml

Incindentally, I am posting from my deck and have gotten bitten a few times by flying insects. Due to my enormous brain and the advancement of human knowledge as a whole, I sprayed myself with Cutter Advanced!. Assuming humans continue to be annoyed by bugs for a few more thousand years, we may use much more advanced insect repellents and insecticides and use it for so long, eventually bugs will stray away from humans altogether and maybe even fear our biological cues (smell, sound, pheromones, what have you). Oh boy, I can't wait for the day. Imagine walking into the woods perfectly naked and having all the bugs for miles flee due to the sense of a human!

[gmalivuk]

There would actually be no reason for them to fear the smell of humans themselves, because it's only these additional chemicals that they have direct reason to avoid. A naked human will remain as scrumptious a meal as ever.

[0.0]

There would actually be no reason for them to fear the smell of humans themselves, because it's only these additional chemicals that they have direct reason to avoid. A naked human will remain as scrumptious a meal as ever.

Ahah, but you forget they have been designed to "sense" us for a lot longer than they have been designed to "sense" the chemicals. So in theory, they could learn to fear our "sense" due to the fact it always leads to the chemicals (for the more recent thousands of years). This of course would be contingent on all humans using the insect repellants for thousands of years. Of course who's to say what would actually go down and how, since evolution can take some very unforseen turns.

edit: I left out an important part of my point. that since they have been trained to sense us for so long, they may be able to sense "human" from farther away than the insect repellent. But since, for thousands of years, the sense of a human always leads to death or something less annoying, they would then learn to avoid us.

[Jonolith]

There would actually be no reason for them to fear the smell of humans themselves, because it's only these additional chemicals that they have direct reason to avoid. A naked human will remain as scrumptious a meal as ever.

Holy Crap this made me laugh. Sweet. Delicious. Human.

The thing is that this whole thread is basically going to turn into a bunch of creative explainations for why certian things evolved or what have you with no real way to say anything one way or the other.

For me, Pineapples. Just... what the hell man? Like... unless you assume that the plant doesn't WANT to be eaten, but then how do you explain plants that ARE easy to eat? Do some plants feel like they need to protect themselves and some plants feel like they shouldn't protect themselves?

Pineapples; God's way of saying "Just don't eat pineapples"

[0.0]

Pineapples, bah! What about coconuts? What can possibly eat a coconut?

I feel a Monty Python reference swelling up inside...

[andqso]

One example of evolution that I find pretty amazing is mitochondria. They are thought to have originated as separate organisms in a symbiotic relationship with cells. They were able to produce energy more efficiently so eventually they were hijacked as the method of energy production and became part of our cells. What I really don't understand is how they could have become integrated into our reproduction.

I don't think they ever really did - IIRC my biology teacher told us when a cell divides each half gets whatever mitochondria happened to be there, and if one of the children doesn't get any it just dies. And since all of a zygote's mitochondria originate in the egg they don't participate in sexual reproduction either.

[rockin2the70s]

One example of evolution that I find pretty amazing is mitochondria. They are thought to have originated as separate organisms in a symbiotic relationship with cells. They were able to produce energy more efficiently so eventually they were hijacked as the method of energy production and became part of our cells. What I really don't understand is how they could have become integrated into our reproduction.

I don't think they ever really did - IIRC my biology teacher told us when a cell divides each half gets whatever mitochondria happened to be there, and if one of the children doesn't get any it just dies. And since all of a zygote's mitochondria originate in the egg they don't participate in sexual reproduction either.

Kind of. What you said is true, but they also have their own DNA and reproductive mechanisms independent of our own; the same for chloroplasts. When the cell divides, the mitochondria divide too, though not necessarily at the same time.

[Blipo]

Pineapples, bah! What about coconuts? What can possibly eat a coconut?

I feel a Monty Python reference swelling up inside...

Coconut crabs. Scary shit.

[HistidineTheCat]

Someone explain the platypus for me please!

Seriously: a bill, eggs, fur, webbed feet, and freakin' VENOM in its HIND CLAWS! What the hell, man?

As for mitochondria, that's as much a symbiotic relationship as anything. The mitochondria/chlorophasts have had the majority of their genome translocated into the eukaryotic nucleus. I believe the replication happens at the same time for both the cell and the organelles. I'll have to look that up, though.

[andqso]

Wikipedia says:

Mitochondria divide by binary fission similar to bacterial cell division; unlike bacteria, however, mitochondria can also fuse with other mitochondria.[42][57]. The regulation of this division differs between eukaryotes. In many single-celled eukaryotes, their growth and division is linked to the cell cycle. For example, a single mitochondrion may divide synchronously with the nucleus. This division and segregation process must be tightly controlled so that each daughter cell receives at least one mitochondrion. In other eukaryotes (in humans for example), mitochondria may replicate their DNA and divide mainly in response to the energy needs of the cell, rather than in phase with the cell cycle. When the energy needs of a cell are high, mitochondria grow and divide. When the energy use is low, mitochondria are destroyed or become inactive. In such examples, and in contrast to the situation in many single celled eukaryotes, mitochondria are apparently randomly distributed to the daughter cells during the division of the cytoplasm.

So in multicellular organisms it was no longer necessary to make sure cells ended up with mitochondria every time, which makes sense if you think about it. I hadn't realized that so much of the mitochondrial DNA had migrated to the nucleus, though. Pretty cool.

Fun fact: platypi (platypuses?) have ten sex chromosomes.

[Eisen Feuer]

(referring back to the topic—not others' posts)


Taste buds.

[gmalivuk]

For me, Pineapples. Just... what the hell man? Like... unless you assume that the plant doesn't WANT to be eaten, but then how do you explain plants that ARE easy to eat?

Same way you explain the fact that some animals have shells and some don't? In other words, different species have different selective pressures pushing evolution in different directions. No big surprise there.

[Interactive Civilian]

For me, Pineapples. Just... what the hell man? Like... unless you assume that the plant doesn't WANT to be eaten, but then how do you explain plants that ARE easy to eat? Do some plants feel like they need to protect themselves and some plants feel like they shouldn't protect themselves?

Remember, fruits are for plant reproduction. The high nutrient, high energy sweetness of fruits tends to serve two main functions: dispersal or nourishment for the seeds.

Dispersal: a fruit tastes good, so an animal eats it. In doing so, the animal disperses the seeds either through passing them through the digestive system or by carrying the fruit and dropping the uneaten seed portions somewhere else.

Nourishment: as the fruit breaks down around the seeds, it leaves a lot of nutrients for the growing seedling to use to start becoming a mature plant.

Some combination of either, combined with variation thoughout history and different selective pressures, can pretty much explain the fruit.

Pineapples? Given that they are so difficult to eat, I would guess that their tasty goodness is to nourish the seeds and get them started on their lives.

Back to the original question...

There are no evolved traits that I find hard to fathom. Why not? Because they exist. Life seems to pull off some pretty creative ways at solving problems and increasing fitness, and I have no reason to believe anything other than natural processes led to those solutions. *Basically*, all you have to do is look at the niche an organism occupies and you can probably glean some of the selective pressures that allowed it to survive while others didn't (yes, it's not always that clear, but a combination of looking at the current niche, looking at the biological, geological, meteorological, etc. histories of an ecosystem, etc. etc. can usually paint a pretty good picture of why/how something is the way it is).

[blanksy]

It seems like pandas should have been extinct a long time ago because they don't have enough sex.

[gmalivuk]

They don't have enough sex at all, or they don't have enough sex in captivity? Because there are many many animals that have a lot of trouble breeding in captivity.

[proof_man]

edit

[iop]

i've always been curious about the evolution of fangs that inject venom. i'm not sure how the mechanism for delivering poison through the teeth could have been beneficial before it was fully operational or how the modified teeth and glands developed in a coordinated fashion.

First, you start to produce poisonous saliva. Then you start to have a groove in one or several of your teeth (mambas, adders). Then the groove gets covered (vipers). No coodrinated development needed, functional at every step.

[gmalivuk]

Yeah, the fact that some snakes are "still" in the stage of having a groove rather than a closed-off vessel through the tooth suggests pretty strongly that this was an intermediate phase for those species that do inject venom directly.

[mdyrud]

How about the bombardier beetle? I don't get how it could have both chemicals appear at the same time, and I don't think either chemical is useful on its own.

[iop]

How about the bombardier beetle? I don't get how it could have both chemicals appear at the same time, and I don't think either chemical is useful on its own.

Quinones (one of the two classes of chemicals) are bitter, and useful on their own. Hydrogen peroxide is something you don't want to ingest either.

TalkOriginshas a list of several steps on how it may have happened:

1. Quinones are produced by epidermal cells for tanning the cuticle. This exists commonly in arthropods. [Dettner, 1987]

2. Some of the quinones don't get used up, but sit on the epidermis, making the arthropod distasteful. (Quinones are used as defensive secretions in a variety of modern arthropods, from beetles to millipedes. [Eisner, 1970])

3. Small invaginations develop in the epidermis between sclerites (plates of cuticle). By wiggling, the insect can squeeze more quinones onto its surface when they're needed.

4. The invaginations deepen. Muscles are moved around slightly, allowing them to help expel the quinones from some of them. (Many ants have glands similar to this near the end of their abdomen. [Holldobler & Wilson, 1990, pp. 233-237])

5. A couple invaginations (now reservoirs) become so deep that the others are inconsequential by comparison. Those gradually revert to the original epidermis.

6. In various insects, different defensive chemicals besides quinones appear. (See Eisner, 1970, for a review.) This helps those insects defend against predators which have evolved resistance to quinones. One of the new defensive chemicals is hydroquinone.

7. Cells that secrete the hydroquinones develop in multiple layers over part of the reservoir, allowing more hydroquinones to be produced. Channels between cells allow hydroquinones from all layers to reach the reservior.

8. The channels become a duct, specialized for transporting the chemicals. The secretory cells withdraw from the reservoir surface, ultimately becoming a separate organ.

This stage -- secretory glands connected by ducts to reservoirs -- exists in many beetles. The particular configuration of glands and reservoirs that bombardier beetles have is common to the other beetles in their suborder. [Forsyth, 1970]

9. Muscles adapt which close off the reservior, thus preventing the chemicals from leaking out when they're not needed.

10. Hydrogen peroxide, which is a common by-product of cellular metabolism, becomes mixed with the hydroquinones. The two react slowly, so a mixture of quinones and hydroquinones get used for defense.

11. Cells secreting a small amount of catalases and peroxidases appear along the output passage of the reservoir, outside the valve which closes it off from the outside. These ensure that more quinones appear in the defensive secretions. Catalases exist in almost all cells, and peroxidases are also common in plants, animals, and bacteria, so those chemicals needn't be developed from scratch but merely concentrated in one location.

12. More catalases and peroxidases are produced, so the discharge is warmer and is expelled faster by the oxygen generated by the reaction. The beetle Metrius contractus provides an example of a bombardier beetle which produces a foamy discharge, not jets, from its reaction chambers. The bubbling of the foam produces a fine mist. [Eisner et al., 2000]

13. The walls of that part of the output passage become firmer, allowing them to better withstand the heat and pressure generated by the reaction.

14. Still more catalases and peroxidases are produced, and the walls toughen and shape into a reaction chamber. Gradually they become the mechanism of today's bombardier beetles.

15. The tip of the beetle's abdomen becomes somewhat elongated and more flexible, allowing the beetle to aim its discharge in various directions.

This is quite a fun thread. I didn't know about the bombardier beetle before I asked the internet about it.

[HistidineTheCat]

Thanks andqso, and good find.

I'll bet higher eukaryotes don't need to regulate mitochondrial division in mitosis because any cell that doesn't have mitochondria will simply die and be replaced. Probably this doesn't happen often, because each cell has dozens if not hundreds of mitochondria. Law of averages says each daughter cell is almost certain to get at least a handful of the things.

Still can't figure out the platypus (didn't know about the 10 sex chromosome thing - that's wild!), but the wikipedia page gives hints. Apparently they're over 100,000 years old, with "close" relatives Teinolophos and Steropodon being over 110 million years old. The genome was just published (a draft) last May, so maybe we'll get some more answers soon?

Linky: http://en.wikipedia.org/wiki/Platypus#Evolution

[Roland Lockheart]

Pineapples, bah! What about coconuts? What can possibly eat a coconut?

I feel a Monty Python reference swelling up inside...

Very few things can eat a coconut, which is the point. Coconuts are not dispersed by bird droppings like other seeds (obviously) but instead grow where they fall or find their way into the ocean to drift between islands or land masses. The thick husk protects the coconut from the ordeal of floating at sea for a long period of time.

[andqso]

Still can't figure out the platypus (didn't know about the 10 sex chromosome thing - that's wild!), but the wikipedia page gives hints. Apparently they're over 100,000 years old, with "close" relatives Teinolophos and Steropodon being over 110 million years old. The genome was just published (a draft) last May, so maybe we'll get some more answers soon?

Linky: http://en.wikipedia.org/wiki/Platypus#Evolution

I don't think it's very well understood (GAPS IN THE FOSSIL RECORD! EVIDENCE FOR CREATION!), but as far as I've been able to figure out the monotremes (the egg-laying mammals) are thought to have diverged early on in the mammal tree when "mammals" still possessed a number of reptilian features. So monotremes have nipples, but the tissue isn't erectile; they have vaginas, but it's the same hole as the urethra and the anus (ick); they nurture their children internally for longer then reptiles, but they still come out in eggs.

The "bill" is actually a single organ covered in skin and sensory tissue and exapted (as far as I can tell) from the nose; contrast with the beaks of birds which are made of keratin and open to reveal the mouth.

Still haven't figured out the venomous ankles or the electroreceptors on the beak.

These things are SO COOL.

[Interactive Civilian]

These things are SO COOL.

Yes, they are. If it were creationism, then they were certainly made of the spare parts that were left over from everything else.

They look like they were designed by 5th graders.

"Hey, check out this hairy little thing I drew!"
"Cool, but it's too normal looking. I know! Make it look like a duck."
"Hahaha! Yeah! Now it looks all goofy though. I think other animals would pick on it."
"You know what it needs? Poison spines!"
"That would be AWESOME!"
"Put them on the back legs so it can do poisonous knee drops onto unsuspecting bears."

[psyck0]

To the OP: Your examples (if used to state that evolution was wrong) fall into the "I can't imagine how it happened, therefore it cannot have happened" method of 'proof', which is completely flawed. Remember that evolution works in tiny, tiny, TINY steps. Imagining such a gradual process can be hard, but when the mechanism is found it will ALWAYS seem astonishingly simple BECAUSE evolution has to work with such small steps. There are no big changes that just spring into being, and so the process HAS to be simple and logical. That is why everyone is so amazed at how evolution can be so 'simple', and yet show such dramatic results.

There are probably a few exceptions that I don't know about/can't remember right now.

[Mr. Beck]

To the OP: Your examples (if used to state that evolution was wrong) fall into the "I can't imagine how it happened, therefore it cannot have happened" method of 'proof', which is completely flawed. Remember that evolution works in tiny, tiny, TINY steps. Imagining such a gradual process can be hard, but when the mechanism is found it will ALWAYS seem astonishingly simple BECAUSE evolution has to work with such small steps. There are no big changes that just spring into being, and so the process HAS to be simple and logical. That is why everyone is so amazed at how evolution can be so 'simple', and yet show such dramatic results.

There are probably a few exceptions that I don't know about/can't remember right now.

You apparently missed the whole "I believe in and am not disputing evolution" bit. This is just a fun thread for the discussion of seemingly improbable evolutionary biology.

In that vein, how in the hell did we get bats? With "sonar", no less!

[HistidineTheCat]

To the OP: Your examples (if used to state that evolution was wrong) fall into the "I can't imagine how it happened, therefore it cannot have happened" method of 'proof', which is completely flawed. Remember that evolution works in tiny, tiny, TINY steps. Imagining such a gradual process can be hard, but when the mechanism is found it will ALWAYS seem astonishingly simple BECAUSE evolution has to work with such small steps. There are no big changes that just spring into being, and so the process HAS to be simple and logical. That is why everyone is so amazed at how evolution can be so 'simple', and yet show such dramatic results.

There are probably a few exceptions that I don't know about/can't remember right now.

Mr. Beck already pointed out that you completely missed the point of the thread. But I gotta also point out that no, evolution is NOT simple. It is not even close. In fact, evolution is the single most complicated thing I have ever come across. If you think it's simple, then you haven't REALLY studied it.

Evolution isn't simply a series of single-nucleotide polymorphisms in coding sequences genetically drifting towards a superior critter. Evolution happens through gene duplications, truncations, rearrangements, and homologous crossovers. It happens through exon splicing, gene sharing, DNA transferral, viruses, and transposons. A significant portion of evolution is shifts in regulation under different cellular conditions. Gene expression at different times in development can drastically change how a critter looks, or it can create entirely new uses for old proteins (gene sharing). These changes can be in any kind of regulatory gene (or a DNA region to which the regulatory protein binds) - look up Hox genes, gap genes, pair-rule genes, segment polarity genes, maternal-effect genes.

There is nothing simple about evolution.

I'd recommend the book Gene Sharing and Evolution by Piatigorsky if you're interested in capturing just a tiny snippet of how complicated evolution is.

[0SpinBoson]

They don't have enough sex at all, or they don't have enough sex in captivity? Because there are many many animals that have a lot of trouble breeding in captivity.

Regarding Pandas, the problem I see with them is that they don't recognize their babies are being part of them. Seriously, I saw a video of a mother panda smacking her newborn around the cage -- they had to go in and rescue it. How the hell does that survive?

[crowey]

They don't have enough sex at all, or they don't have enough sex in captivity? Because there are many many animals that have a lot of trouble breeding in captivity.

Regarding Pandas, the problem I see with them is that they don't recognize their babies are being part of them. Seriously, I saw a video of a mother panda smacking her newborn around the cage -- they had to go in and rescue it. How the hell does that survive?

captive behaviour != wild behaviour.

Wild populations of pandas are actually doing OK (considering the habitat destruction/fragmentation and all the illegal hunting), they breed at an alright rate and have decent survival.

Captive pandas won't shag, and if they do they kill the babies. To me, that is an animal that shouldn't be kept in captivity.

Edit: I should say, pandas are by no means doing well in the wild, but I mean the breeding issues they have in captivity don't seem to exist outside of zoos.

[Roland Lockheart]

My question: the lamprey. What is it? It is a long rubber tube filled with teeth and an insatiable appetite for blood. WTF!?!?!?

[Interactive Civilian]

In that vein, how in the hell did we get bats? With "sonar", no less!

Again, while I don't find any of it unfathomable, in this case, I'd be curious... which evolved first? sonar or the ability to fly? Or did they evolve simultaneously?

You can get a lot of interesting speculation no matter which option you pick. Anyone have any real information?

[qetzal]

Recently discovered fossil evidence also says flight before sonar in bats. See http://scienceblogs.com/zooillogix/2008/02/first_flight_then_radar.php and http://scienceblogs.com/loom/2008/02/13/a_hairy_archaeopteryx.php for nontechnical discussions.

[gedtheflayer]

It's amazing the sort of weird stuff evolution can do. Right now the lab I'm in is working with pea aphids, which have symbiotic bacteria (called Buchnera) that are passed down mother to daughter and stored in a special organ specifically evolved to sustain that bacteria. Barring mutation, these bacteria are the same as the ones that inhabited the aphids since their species branched off. Since they have a mostly parthinogenetic life cycle (the mother spawns genetically identical daughters) you have a bunch of aphid clones bouncing around. The odd thing is that there are different "biotypes" of these aphids; they feed on completely different plants, and thus don't often interact to mate, but they haven't quite speciated yet. This is cool because some research in Japan has shown that in some cases these biotypes can be induced by different varieties of bacteria hopping into the specialized organ along with the more traditional Buchnera and adding new digestive enzymes into the mix.

As for what baffles me about evolution, I am utterly perplexed by the transition from prokaryote to eukaryote. The strangest bit for me is making the leap from circular to linear DNA, since the organism would be discarding the plasmid system, which was integral to survival and competition in the prokaryotic world.

[0.0]

with all the amazing changes that take place, maybe the more amazing is the "perfect" animals that somehow remain unchanged for 10's of 1000's of years. I'm talking about the great white shark, the horseshoe crab, the crocodile and many more. These living fossils seem to have gotten to such a "perfect" state when compared to their surroundings that evolution seems to have a hard time making any new variations. Imagine how many species that at some point was prey to the great white shark that have evolved, existed and died out. But the shark remains and just hunts, kills and eats whatever evolution throws at it.

Man getting the big brain: I've read that Africa is the most theorized place of origin for the first humans. So I was thinking what about africa would cause smart social primates of yesteryear to evolve big brains? One thing about Africa, is there are quite a few successful mammal types that hunt in groups; lions, dogs, hyenas, baboons. This is probably due to the type of prey being of the sort that stays alive mostly through running away as a big group or defending themselves as a group, therefore a single Lion or African dog would have a hell of a time getting kills consistently. And after a kill, they need to work together to defend the kill and devour it in an efficient manner. So I suppose the clever apes learned to work together and any sort of "pack" of these apes that developed a communication method while hunting would instantly get a great advantage over other packs. Once all the packs were using communication, the new skill would clearly develop since it would be so useful. The next logical step of evolution of this sort would be that the "packs" who deduced a better strategy would get the most kills. From that point on, when compared to other evolutionary tracts, it seems clear the smarter the pack the more successful it would become. This being a much bigger influence in survival than say speed or jumping and biting skills, would lead to a quick evolution of the brain while the skeletol structures remained very unchanged in relation. Maybe this would have some effect on the missing "links" since we mostly look at skeletol evidence of evolution; which is of course because that is all we can look for!

[gmalivuk]

Even without any separate evolutionary evidence, I would naively assume flight before sonar, simply because some bats are diurnal and rely primarily on their eyes instead of echolocation, while no non-flying species closely related to bats has sonar.

My question: the lamprey. What is it? It is a long rubber tube filled with teeth and an insatiable appetite for blood. WTF!?!?!?

The lamprey, like all parasites, must originally have evolved as an independent organism. Probably once it found a niche parasitizing other animals, a number of traits became unnecessary, and were gradually lost over time as natural selection favored those genomes that sapped less energy growing and maintaining pointless parts and used more to improve its efficiency as a parasite.

[qetzal]

(N)o non-flying species closely related to bats has sonar.

Actually, this appears to be untrue. The first link in my previous comment states that some shrews use echolocation, and bats are supposed to have evolved from shrew-like ancestors.