savanna

All posts tagged savanna

Credit Marjaree Mason Center – CC-BY-SA

Here is the list of the ten posts on Green Comet that got the most visits in 2018.


1. Spanking for Love

Once again Green Comet seems to be a gateway for people who want to learn about spanking their women. Humans are funny little things, aren’t they?


2. Bipedal – The Savanna Theory

Judging from the pattern of hits, I’m guessing that a lot of children find this post after getting a school assignment.


3. Home Page
This makes sense, since it’s the landing page for the site.


4. Ants in the Devil’s Garden

It’s a fascinating story, so I’m not surprised at the interest in it. It’s interesting to speculate about the search parameters that led here. There are some good comments, too.


5. Most Unpleasant Sounds

Once again, how do people end up here? What is the interest in unpleasant sounds?


6. Downloads

This is gratifying. Since the purpose of the Green Comet website is to provide a home on the internet for the Green Comet trilogy, I am pleased that so many people go to the downloads page. In fact, you should do that as soon as you finish reading this post. Download everything. It’s free.


7. Bipedal – The Aquatic Ape Theory

This one is probably linked to #2. They are closely related ideas.

Credit Craig Sunter – CC-BY


8. Cirrus Homogenitus

Everyone loves clouds, and this one is probably particularly interesting because it’s one of the rare new ones designated by the World Meteorological Organization in their International Cloud Atlas.

Photo credit – Ross Cooper


9. Altocumulus Lenticularis

More clouds, and these ones are popular for their striking appearance and their counter-intuitive behavior.


10. Altocumulus Castellanus

More clouds, and again very distinctive in their appearance.

So, that was 2018. I think I’m safe in predicting that the list for 2019 will be similar.

rjb

The Waterside Ape BBC Radio 4 reply to Alice Roberts and Mark Maslin

In my recent post, Aquatic Ape Attacked Again, I pointed to an article that purported to falsify what is commonly referred to as the Aquatic Ape Theory. My post pointed out a few of the shortcomings of that article. Now here’s a link that does a much more thorough job of it.

Source: A reply to Alice Roberts and Mark Maslin

If you’re interested in the theory, or in paleontology in general, I recommend checking out this latest development.

rjb

David Attenborough’s latest BBC documentary indulges wishful thinking over evidence.

Internet magazine, The Conversation, has published an article by authors Alice Roberts and Mark Maslin entitled “Sorry David Attenborough, we didn’t evolve from ‘aquatic apes’ — here’s why.” They begin by claiming that the Aquatic Ape Theory (AAT) suggests that a whole raft of our biological features stem from an aquatic phase in our evolution. Then they go on to imply that the “hypothesis” says that everything about those features could only have come about due to time spent in the water. Once they have set up this implausible falsehood, they proceed to cherry-pick it apart, beginning with the fact that the “hypothesis” had its beginnings a long time ago, and we’ve learned a lot since. They imply that the AAT is the plaything of fuzzy-thinking amateurs, while they represent clear-headed professionalism. In other words, it’s the same old thing all over again, only from a new generation of Savanna apologists.

Like their predecessors, they portray the AAT as an unscientific Just So Story, and say that all of the anatomical features can just as easily be attributed to other hypotheses. We’re left to presume that these other hypotheses are not Just So Stories, but Real Science. They run through all their Straw Men, showing that there are plausible explanations for all of them, thus implying that the Aquatic Ape explanations are not plausible. Then they accuse the proponents of the AAT of trying to use it to explain everything. That’s a typical ploy. You ask your opponent to support their argument, then when they’ve done so, you accuse them of overdoing it. It’s very handy. Either they don’t have enough, or they have too much. You simply ignore the sweet spot in between, all the while highlighting the weaker arguments and ignoring the stronger ones.

Their conclusion is nothing more than a reiteration of their opinions and beliefs. There’s nothing new here. It’s just the same old thing dressed up in new clothes. They say they’re making use of new knowledge and new ideas, but it’s obvious they’ve restricted themselves to those they agree with.

See for yourself.

Source: Sorry David Attenborough, we didn’t evolve from ‘aquatic apes’ – here’s why

rjb

Bipedal skeleton
See also parts two and three.

There are many hypotheses about the fact that humans walk on two legs. We aren’t the only ones to do so. Birds are bipedal, that is they have only two feet. Many dinosaurs were bipedal, for instance the Tyrannosaurus Rex and the velociraptors. Fossils of the earliest dinosaurs are from small predators with two legs. Birds are believed to have descended from at least one line of bipedal dinosaurs. But amongst mammals humans are with only a few who regularly get around on two feet.

Other mammals include the giant pangolin, an anteater. When it’s down on all fours it carries most of its weight on its hind legs, and it often walks upright, using its tail for balance. Also in this group are the macropods, meaning animals with big feet. These are the kangaroos, wallabies and other hoppers. Other mammals use limited forms of bipedalism while using their front paws, for example rats and beavers. Some do it to better view their surroundings, like ground squirrels and meerkats. Some antelopes and deer stand on their hind legs to feed from trees.

Although we have a lot of company, no other mammal has specialized its bipedal locomotion to the degree of our upright stride. Our feet can’t grasp things like those of our primate cousins. Our legs are so long and our arms so short that we can’t walk on all fours with any efficiency. Our spines, pelvises, knees and ankles are best adapted for an upright striding gait.

So, how did we get this way? Any explanation for how we diverged from our primate cousins has to account for a lot of obvious differences between us and them. Our closest relatives among Earth’s other animals are the primates – that’s all the monkeys, lemurs, gibbons, apes and so on. Among the primates, the other apes are most like us – orangutans, gorillas, gibbons and chimpanzees. Our closest relatives of all are the other great apes – orangs, gorillas and chimps – none of which is primarily bipedal. The gibbons are classified as lesser apes. Although they are more similar to us than, say, a trout, there are obvious differences between us and our ape relatives. While we move on the ground on two long, straight legs, the others show more quadrupedal locomotion, having longer arms and shorter legs. We have longer, stronger thumbs and shorter, straighter fingers. We have larger brains relative to our body mass. We have much less hair than the rest of the great apes.

There have been many suggestions for our uniqueness, with wildly varying levels of plausibility. It’s likely that no single explanation can account for it on its own. The most widely held consensus is the Savanna Theory, which holds that we developed bipedal locomotion to deal with the grassland, or Savanna, that was spreading about that time. Before about seven or eight million years ago all of the great apes lived in a great forest that covered much of the equatorial and sub-equatorial Earth. Then there was a change in the climate. It got drier and the forest began to recede, with patches of grassland growing between the trees. While the other great apes continued with their traditional lifestyle as forest dwellers, the Savanna Theory holds that our ancestors began to exploit both the old habitat in the trees and the new opportunities in the grass. That’s when our forebears and those of the chimpanzees split from a common ancestor and evolved in different directions. As our ancestors had to move farther between clumps of trees as their forest was shrinking, an upright posture would have helped in many ways. It would improve their view in tall grass. It would reduce the amount of their skin exposed to the sun. It would get their heads above the hot boundary layer near the ground, helping them stay cooler. Also for cooling out there under the blazing sun, they lost their body hair. In addition, they might have used their hind limbs for standing and walking more as they used their hands for carrying things across open ground.

Some other advantages came from this adaptation. It provides a better posture for feeding from trees while standing on the ground. Being upright makes wading in water easier and safer. Our long, strong thumbs and short, straight fingers evolved as we swung in the trees less. Other great apes have curved fingers which facilitate hanging from branches. The unique anatomy of our hands makes them stronger and more versatile in a wider range of activities. Our larger brains are partly the result of a positive feedback loop between our nimble hands and a growing intelligence. As our greater dexterity improved our diet, our better brains improved our abilities.

The question of human bipedalism holds an unspoken assumption that we evolved the trait while the rest of the apes didn’t. We may have to examine that assumption. To this day large primates like orangutans walk upright on their tree branches. Their knee joints are so similar to ours that we’d have to say that they evolved for an upright stance. It’s an adaptation that shows up in the fossil record twenty-one million years ago, long before our ancestors were walking on the ground. There’s a growing suspicion that other primates like gorillas and chimpanzees evolved their quadrupedal locomotion on the ground while our forebears stuck with the bipedalism learned in the trees. Maybe we should be asking why they did that instead.

That’s a brief look at some of the features of the Savanna Theory. Next time we’ll look at another explanation, the Aquatic Ape Theory.

rjb