Thread: Ardi and Beyond

With the discovery of Ardi and other skull fossil remains dating back 4.4 - 6 million years ago I have been highly interested in obtaining knowledge of theories that explain the time before Ardi. Obviously the knowledge of Ardi is still increasing day by day, can anyone share some theories of human ancestry formation? Is there any evidence that we may have come from a water bound organism yet? Where does the evolution begin? For example Darwin’s theory that we are ancestors of apes: What are apes ancestors of? Any thoughts?

Darwin was actually of the opinion that modern apes evolved further since a split from humans, presumably to become more brutal. The teeth of Ardi and even earlier Ardipithecus kadabba show Darwin guessed right. Their relatively short, blunt canine teeth are little more offensive than modern humans'.

A lot of attention has been given chimpanzee gender relations, manifested in male's especially long sharp canines which they snarl and bite with. Males employ these teeth to threaten young and females. Now it appears this behaviour is essentially a chimp development, so we shouldn't take it as insight into our own social evolution.

I'll speculate defenceless Ardi was bullied by the females during their bitchy time of the month. Heh. Just to troll up some debate.



Regarding aquatic theory. I think this suffers on both sides from either/or thinking. Ardi was an all-terrain vehicle. It was not real great at anything, because it could navigate a lot of different environments. It was also an omnivore. So I imagine Ardi moving through a mixed terrain, where one minute it's climbing over logs and litter, another it's crossing a clearing, and another minute it's wading through a lake.

I think there's great tactical advantage in capacity to foil predators by retreating to terrains where they're helpless. Humans seem to know this and exploit it instinctively: watch kids play tag around a jungle gym, note their games of "can't cross the sand" etc. Entering water is a "cheat" we naturally employ, and I guess many of our ancestors owe their lives to this ability.

I have alwasy been sceptical of the water theory, simply because there have been no hominid fossils found in marine sediment. Forming fossils is really unusual, and the significant number of pre-human fossils discovered reveals a major amount of effort on the part of researchers. Yet, the easiest and most common way of forming fossils is when a body sinks in the sea and is covered by marine sediment. We have never seen such a fossil, and it should be the most common, if our ancestors spent time in the sea.

Like I said, the aquatic theory is often framed to paint an unrealistic picture:

Originally Posted by mustbesomething

a water bound organism

Originally Posted by skeptic

if our ancestors spent time in the sea

Do beavers, hippos, or raccoons fit those descriptions? Yet they're clearly adapted to feed from the water, and readily escape predation by switching elements.

I think another way of looking at it, is by contrasting chimps to see which niches they left open for us, as our specialties diverged from a common ancestor. Chimps are shy of the water. In fact, if a chimp is harassing you, a good solution is to walk a bit into a pond. I think that marshes and shallows offered an underexploited niche the human line took up. I think that since humans civilized and left the niche again vacant, bonobos represent a recent divergence to eventually fill it. So I predict bonobos will specialize (actually generalize) apart from chimps in roughly the same way humans did.

Originally Posted by mustbesomething

I have been highly interested in obtaining knowledge of theories that explain the time before Ardi. Obviously the knowledge of Ardi is still increasing day by day, can anyone share some theories of human ancestry formation?

Going back 65ma our ancestors were the Prosimians. From these diverged the Old world and New world monkeys 25ma. The lesser apes evolved from the Old world monkeys 18ma. Great apes descended from the New world monkeys 12ma.

The Orangutan and Gorilla appear 10ma. 6-7ma saw the divergence of Chimps and Humans.

great replies, thank you.

"From these diverged the Old world and New world monkeys 25ma"

Taking the new world and old world monkeys into consideration and going back to my original statement regarding the emergence of our ancestors from a marine habitat, is there any evidence that a marine species ever had downward facing nostrils or opposable thumbs?

Originally Posted by mustbesomething

Taking the new world and old world monkeys into consideration and going back to my original statement regarding the emergence of our ancestors from a marine habitat, is there any evidence that a marine species ever had downward facing nostrils or opposable thumbs?

In short: no. The "aquatic ape" hypothesis has had its day and is now considered by paleoanthropologists to generally be pseudoscientific where it still crops up. This is because given the actual evidence that exists, to substantiate an "aquatic ape" explanation would require many assumptions to be true that are neither present in the fossil and material records nor compatible with evidence that already exists in these records.

I recommend authors like J.G. Fleagle (Primate Evolution and Adaptation) or Richard Klein (Human Career), who both give very good, well-referenced overviews of primate and hominid evolution. These are both available at most moderate libraries and earlier than current editions can be found at discount at used bookstores or Amazon.

Originally Posted by SkinWalker

The "aquatic ape" hypothesis has had its day and is now considered by paleoanthropologists to generally be pseudoscientific where it still crops up.

This is really unfair IMHO. Because no one argues adaptations to be also capable of wading and swimming "pseudoscience". If I claim it adaptive to be able to climb a tree sometimes, no one laughs at me.

The hostility to Morgan is a lot like hostility to Freud, where everyone accepts his theory of a subconscious yet insist the man was full of crap. Somehow we've come to accept our ancestors mainly foraged around water bodies, ate a lot of shellfish, and freely migrated across rivers, yet Morgan's off her rocker. And note the original hypothesis was so modest to suppose a few hours per day at most foraging shallow water snails and clams (this was withheld 30 years by Alister Hardy for fear of ridicule). Today it seems plausible.

Mustbesomething, as long as you don't mention trigger words like AAT or start comparing us to whales, you're good to go. Just keep in mind the all terrain vehicle Ardi adapted also to many situations. Water adaptations are just part of the generalist/opportunist strategy.