Human evolution: the year 2010 in review (Part 1)

That’s some good-looking gombo, cher!

gumbo
Creative Commons License photo credit: Southern Foodways Alliance

This blog contribution aims to be like a good Louisiana seafood gumbo: thick, hearty, spicy, and made up all kinds of finger-licking ingredients (pun intended). There will be some French, which would be apropos, some Latin as well, and all kinds of discoveries related to human origins, as they transpired this past year. I will follow up with a second part in a week or two with an observation and a comment.

In an earlier blog, “A pinky’s promise,” I wrote about the incredible discovery that was made early in 2010 when DNA analysis was performed on one small finger bone retrieved from a cave in Southern Siberia. The bone dated to a period (50,000 to 30,000 years ago) when all scientists assumed that the only living humans were either Homo sapiens sapiens or Neanderthals (perhaps we should now be saying Homo sapiens neanderthalensis, but I am getting ahead of the game). This first assumption proved to be wrong.

Entrance to the Denisova Cave
Creative Commons License photo credit:ЧуваевНиколай

In 2008, DNA analysis carried out on a single finger bone revealed that there was a third species of human walking the earth at that time. Toward the end of 2010, this view was corroborated by additional DNA analysis of a few teeth that were found in the same Denisova cave. The Max Planck Institute in Leipzig announced that these so-called “Denisovans” represent a new species.
More interesting still, some of their DNA is still around: the “Denisovans” interbred with the ancestors of Melanesians. This implies that at one point, this third species was quite widespread in Asia. If these conclusions hold up, the lesson we should take away from this breakthrough is that every little scrap of evidence counts when studying human origins, even a single tooth, or a finger bone. I wonder how many single finger bones or teeth have been overlooked in the past, or are still awaiting re-discovery in a museum drawer somewhere.

Neanderthals were also in the news this past year. For years, researchers have been vexed by questions such as “Who were these people?”, “Where did they come from?”, “What made them extinct?” and last but not least “Is there a little bit of Neanderthal in (some of) us?”

With regard to the last question, also discussed in earlier blogs, the way in which we answer that question will result in a different scientific (read: Latin) nomenclature for Neanderthal. Allow for the possibility of interbreeding between Homo sapiens and Neanderthals and also agree that their offspring was fertile, i.e., they successfully reproduced, then you would have to refer to Neanderthals as Homo sapiens neanderthalensis. If you disagree with this idea, and think it was unlikely these two populations interbred, or that their offspring was not capable of producing fertile offspring, then you would have to refer to Neanderthals as Homo neanderthalensis. This classifies them as a species separate from modern humans; by definition, species cannot interbreed and produce fertile offspring.

Man
A Happy Neanderthal
Creative Commons License photo credit: erix!

The latter way of thinking was long popular among paleoanthropologists. Now the pendulum is swinging the other way. Scientists at the institute decoded the Neanderthal genome and compared it with that of modern humans. The result? In their words: “By comparing that genome with those of various present day humans, the team concluded that about 1 percent to 4 percent of the genome of non-Africans today is derived from Neanderthals.”  In people speak: up to 4% of a European’s genetic makeup could be inherited from the Neanderthal lineage, now extinct.

Before you check for hair on your knuckles, thank (or blame) a single finger bone and a few teeth, as well as the staff at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany for all this.

Lest we all (well, at least those of us of European descent) break out in hives and run for the nearest hills, scientists were quick to add: “[T]he Neanderthal DNA does not seem to have played a great role in human evolution.”

Certainly, 1 to 4% overlap in genetic makeup is not very much, but it is a whole lot more than we were willing to consider just a year ago. Differences between Homo sapiens sapiens and Homo sapiens neanderthalensis remain significant. The overall physical appearance of a modern human is very different from that of a Neanderthal. In terms of behavior, and cognitive abilities, the two subspecies also appear to be a world apart, never mind they shared portions of our planet.

Comparing Neanderthals and modern humans
One of the areas in which there were both similarities and differences was diet. These insights also came out this past year.  Did you know that Neanderthals ate their veggies? And that they liked to cook them as well? Perhaps you did. However, did you also know that they were not averse from eating each other?

Check back next week to see more on this, when Dirk discusses teeth, DNA, and his own conclusions to 2010 in review.

Lucy’s Great Mystery: How Could Australopithecus Survive and Evolve Into Us?

Part One:

She Should Have Been Caught and E A T E N !

Lucy evolved into us. Really, really (to quote “Shrek.”)

Her species, Australopithecus afarensis, or something extremely close, changed over three million years to become Homo sapiens – the species that includes you and me.

So we should treat Lucy with respect…….

….but wait.  There’s a problem. It shouldn’t have happened. Lucy and her whole species should have been gobbled up by a legion of voracious, bloodthirsty carnivores! She shouldn’t have had any time to evolve at all.

Darwin Makes Sense (usually)

Evolution should be logical – when we have enough data. Textbooks used to say that Lucy evolved from an ancestor who was built like a chimp. But Lucy’s knee and ankle and hip bones were NOT chimp-shaped. The design of Lucy’s joints is very close to what we have – so we know that Lucy walked upright, on just her hind legs, with left and right knees close together.

s-Parade-Blog-ColorFine.  Did leg evolution make Lucy better?  Faster? That’s what we’d expect. But it looks like evolution made Lucy  s l o w e r !  Chimps run very fast and can change direction in an instant. These apes zip around on all fours, running on their knuckles. A modern human has great difficulty catching a running chimp – I know, I used to be a zoo-keeper in charge of three boisterous chimps.

Lucy couldn’t match chimps in speed and maneuverability. Since she walked just on her hind legs, her arms were useless dead weight in running. Plus – she was very short in the legs. Her shins and thighs were far shorter than in modern humans. She was not nearly as fast as we are today.

Why would evolution make Lucy slower?

Lucy – Evolved for Holding Babies on the Open Plains?

The standard theory said that Lucy’s upright posture was fit for moving across savannah, open grassland with scattered trees. She could walk for hours and use her hands to hold her babies or an armful of fruit or a big Pliocene salad or whatever.  Meanwhile, her chimp ancestors stayed in the forest. Sounds good……except we have a huge problem. The savannahs were occupied by a whole host of predators  who would love to eat Lucy and her kind.

In fact, Lucy was evolving during the worst possible time. The australopithecine clan evolved between 5.8 to 1.8 million years ago. This interval produced the scariest variety of big feline meat-eaters the world has ever seen.  Here’s what was out there, ready to catch Lucy and her kin.

Leopards
s-Kitties-Blog-ColorLLeopards are stealth felines who lived with Lucy. They had short, wide paws, flexible legs and body. That’s a build excellent for climbing rocks, hiding in burrows, ascending trees – and sudden ambush! Body weights went from 50 lbs to 200 lbs.

Lions & Tigers
Lucy’s neighbors included lion-like cats, huge predators up to 500 lbs, with massive paws that could swat down a water buffalo. Legs were longer, straighter than a leopard’s and speed over level ground was higher. Because of the great weight, climbing was less agile than a leopard’s.

Dagger-Tooth Saber Cats – Homotheres
Lucy’s world was jam packed with saber-toothed cats. The biggest were the Dagger-Tooths, who were built like a cross between a cheetah and a leopard, with long legs, excellent for fast running with some climbing. Sizes ranged from up to 500 lbs. The jaws were like a rattlesnake’s. They opened so wide that the upper fangs were exposed and ready for action. The upper fangs were long, wide blades with very sharp, saw-toothed edges. Homotheres slashed and stabbed so deeply they could kill an elephant.

Long, muscular necks let saber-cats swing their head down like a battle-ax.

How could Lucy avoid these deadly cats?

Imagine that you are Lucy. You’re waking along the savannah, carrying a load of  melons. Then, without warning…..WHAM!  A leopard leaps on you, bites your neck, and you are leopard-kibbles. Or….you’re resting on a rock when…..WHAM!  A pride of lions jump you and tears you apart. Or….you’re plucking figs from a fig tree when…a Dagger-Tooth jumps up from the tall grass. You try to run as fast as you can….but in ten seconds…WHAM! Zip-Zap!  The cat slices you into bite-sized pieces.

Lucy Defended Herself With Spears?

An old theory says that Lucy’s kind used spears and rocks for defense. But that notion doesn’t work. We find no stone tools at all with Lucy’s bones, not a spear point or a stone knife.  How about a wooden spear? Chimps today make mini-spears from twigs and impale bugs and little furballs. Sure, Lucy might have picked up a branch and chewed the end to make a point.

But if Lucy poked a  Dagger-Tooth in the butt with her spear, she’d only make him mad.

No, wooden spears aren’t enough to drive away lions and leopard and saber-toothed cats.

Conclusion: Lucy and All Her Kind Should Have Been Massacred by The Big Cats.

We’re left with a big problem. How did Lucy get away?

Please! Help our Lucy!!!!!

Send in your suggestions about how to avoid predators!

Interested in learning more about Lucy? Check out my previous blog posts on Australopithecus afarensis migration.

Neanderthal Controversy

As mentioned in a previous post, the question of whether or not Neanderthalers were able to have offspring continues to be hotly debated by scientists. Depending on the answer given, we would have to classify Neanderthalers either as people like us, or people very different from us. Of course, proponents of both of these statements claim they have evidence to back up their very different positions.

Those who suggest that there was interbreeding between our ancestors (Homo sapiens sapiens) and Neanderthalers would label Neanderthal bones as belonging to Homo sapiens neanderthalensis.

With this label, the word “Neanderthalensis” appears in the third position of the nomenclature, which refers to the level of sub-species. This implies that the differences between us and Neanderthalers are so small that they are contained within the range of variation one would expect to find within a species (in other words, we are related to Neanderthals on a sub-species level, rather than being classified as two different species.)

According to this interpretation, the ability to interbreed with modern humans might have also spelled doom for the Neanderthals. But if the two species interbred, why don’t we see the “typical Neanderthal look” today?

As time went by and interbreeding between our ancestors and Neanderthalers continued, the thinking goes that the Neanderthalers’ genetic contribution to each new generation became ever smaller. Eventually, this percentage became so small that all people began to look like humans rather than a Neanderthal individual.

Scientists refer to this scenario as genetic swamping. If this is what happened, it would be possible for the two species to have interbred over many generations, while also explaining why the influence of Neanderthaler genes can’t be seen by the naked eye. A child burial uncovered in Portugal is seen as evidence that “admixture between the two groups must have been significant, at least in such cul-de-sacs as the Iberian Peninsula,” providing more support for this position.

Others disagree and suggest that we use the nomenclature Homo neanderthalensis.

Here the term “neanderthalensis” is in the second position of the nomenclature, referring to the species. This is a scientist’s way to say that the difference between humans and Neanderthalers is at the much more significant species level. This has an important implication: according to these proponents, Neanderthal populations and Homo sapiens populations could not have produced fertile offspring.

Of the two positions just outlined, most scientists prefer the second one and refer to DNA analysis for support. DNA analysis of Neanderthal bones has been undertaken for a while. A comparison of Neanderthal DNA against modern human DNA suggests that there are enough genetic differences to warrant labeling them as a separate species.

Most scientists, therefore, prefer seeing “Homo neanderthalensis” in the scientific literature. Since interbreeding and subsequent genetic swamping cannot occur in this scenario, the disappearance of the Neanderthalers is blamed on outright genocide practiced by our ancestors, or greater hunting skills on the part of the newcomers.

What kingdom are you from?

We’ve seen how Carl Linnaeus’s system classifies Lucy. How is the classification that refers to her different from the one that refers to us?

Applied to humans, a Linnaean chart could be filled out in the following way. (Notice the prevalence of Greek and Latin terminology.)

Domain: Eukaryota – containing all organisms which have cells with a nucleus.

Kingdom: Animalia – including organisms with eukaryotic cells that have a cell membrane but lack a cell wall, are multicellular, and heterotrophic (meaning that they cannot synthesize their own food, as plants do.)

Phylum: Chordata – including animals with a notochord, dorsal nerve cord, and pharyngeal gill slits.

Subphylum: Vertebrata – animals possessing a backbone, which may be made of cartilage, to protect the dorsal nerve cord.

Class: Mammaliaendothermic vertebrates with hair and mammary glands which, in females, secrete milk to nourish the young.

Subclass: Placentalia – including animals that give birth to live young after a full, internal gestation period.

Order: Primates – including animals with a collar bone, eyes that face forward, grasping hands with fingers, and two types of teeth: incisors and molars. 

Family: Hominidae – including primates with upright posture, a large brain, stereoscopic vision, a flat face, and hands and feet with different specializations (such as grasping and walking).

Genus: Homo – having an s-curved spine, “man.”

Species: Homo sapiens – characterized by a high forehead, well-developed chin, and thin skull bones.

While Latin and Greek are no longer used when scientists write or e-mail each other, these languages continue to survive in the names given to plants and animals. For those few among us who did study Latin and Greek, here is one practical application of hours and hours of learning vocabulary and conjugating verbs: it allows one to more easily see the origins of the terms used and thus facilitates our understanding of what is meant.

For all those others who did not study these ancient languages, consider the old saying “The more it changes…”