Tag Archives: evolution

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

Published by on in Anthropology
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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.

Sea Rex 3D swims into IMAX!

Published by on in Giant Screen Theatre
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Explore an amazing underwater universe inhabited by larger-than-life creatures that ruled the oceans millions of years ago in Sea Rex 3D – now showing in HMNS IMAX!.

Mosasaurus hoffmannii skeleton on display at the
Maastricht Natural History Museum,
The Netherlands

Guided by Georges Cuvier, considered by many to be the father of paleontology, viewers learn about predators such as the ichthyosaur, plesiosaur, and mosasaur. These ancient creatures could grow up to 50 feet and could weigh as much as 15 tons.

Learn about the Triassic, Jurassic, and Cretaceous eras and how life evolved in the deep oceans of Earth. See a mosasaur battle the Great White Shark’s ancestor and witness the mating habits of the plesiosaur.

You’re going to love the film’s time line of the history of the Earth, showing the evolution of the first single cell organisms to the mammals that evolved and began to walk on land. What I found fascinating is the amount of time each of the dinosaurs ruled the world in comparison to humans. Dinosaurs walked the earth for over 160 million years, while humans have only been around for about 200,000 years comparatively.

Evidence of giant marine predators were first discovered in a mine shaft in the Dutch city of Maastricht in 1770, when the partial skull of a Mosasaurus hoffmannii was uncovered. Sea Rex 3D takes you on a journey from the creation of earth until the meteor that killed off 95% of life 65 million years ago. Don’t miss this incredible story about our planet’s history and the monsters that ruled the sea for over 120 million years.

Can’t see the video? Click here.

Sea Rex 3D is now showing in the Wortham IMAX Theater. See show times on our Film Schedule.

How To Evolve a Wing

Published by on in Paleontology
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Our Archaeopteryx show has bedazzling fossils – the only Archaeopteryx skeleton in the New World, complete with clear impressions of feathers. Plus frog-mouthed pterodactyls, fast-swimming Sea Crocs, and slinky land lizards. Today we learn the different ways in which wings evoloved on various prehistoric creatures.

Solnhofen show us three ways for Darwinian processes to construct a wing from a normal arm

Dactyls:
Dactyls evolved from very close relatives of early dinosaurs. The dinosaurs and their crocodilian kin are archosaurs. Archosaurs developed a unique asymmetry in the hand. Primitive reptiles, like today’s lizards, have five fingers, each with a strong claw. In archosaurs the outer two fingers are weak and have no claw at all.

Crocodilians and many dinosaurs kept this arrangement -  for example, stegosaurs and Triceratops had five fingers and three claws on the inner fingers. Meat-eating dinosaurs usually evolved three-fingered hands, doing away with those outer two claw-less fingers.

‘Dactyls evolved their archosaur hand in a different manner: they lost the pinky (the outermost finger). The claws on the inner three fingers were strong – useful for climbing trees and the sides of cliffs. The fourth finger evolved into an organ we see in no other creature: Finger four became immense, as thick as the thigh or thicker. The finger could be folded back where it joined the wrist for walking on the ground. When flying, the giant finger four was stretched outwards.

 Schematic of a generic pterosaur wing, pencil drawing, digital coloring
Creative Commons License photo credit: Arthurweasley

Solnhofen fossils showed that the wing surface was attached to the finger four and to the sides of the body and the inner edges of the hind leg. So ‘dactyls could flap like a bat – using up and down strokes of both arm and leg to make the power stroke.

Dinosaurs and Birds:

 Archaeopteryx

Birds evolved their wing by another wonderfully unique method. Their hand bones were 99% identical to those in small meat-eating dinosaurs. Only the three inner fingers were retained. Darwinian processes had clipped off the pinky and fourth finger. Solnhofen fossils prove that specialized wing feathers were attached to the second finger. So Archaeopteryx flew with the feathered arm.

Raptor-type dinosaurs, like Velociraptor and Microraptor, had evolved feathers very like those of birds. But these small dinosaurs evolved hind-leg wings to assist the arms. Flight feathers were attached to knee and shin as well as to the forelimb. When a tiny raptor-like dinosaur evolved into Archaeopteryx, the feathers were lost from the hind-legs, leaving just the arm to do the work of flying.

Bats:

Bats are specialized mammals and no bats had evolved in the Jurassic. The first bats appear much later, about 55 million years ago.

Bats use strong skin to make the wing. But unlike ‘dactyls, who evolved just one finger to support the wing surface, bats use three or four fingers to spread the wing and control the wing in flight.

Don’t miss Archaeopteryx: Icon of Evolution, currently on display at HMNS. Want to learn more? Check out our previous blogs on Archaeopteryx.

The Man Who Made Fossil Fish Famous

Published by on in Paleontology
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Our Archaeopteryx show has bedazzling fossils – the only Archaeopteryx skeleton in the New World, complete with clear impressions of feathers. Plus frog-mouthed pterodactyls, fast-swimming Sea Crocs, and slinky land lizards. Today we learn about the Louis Agassiz and his theories.

Louis Agassiz (1807-1873)

Paris and the Lure of Fish, 1836
Agassiz grew up in Switzerland where he excelled as a student in  chemistry and natural history. He went to Paris to study fish fossils under the Father of Paleontology, Baron Georges Cuvier. The geological history of fish seemed muddled at the time. Agassiz brought order to the fins and scales.

“There’s order in the way fish changed through the ages…” Agassiz concluded. He was the first to map out the long history of fish armor, fish jaws and fish tails.

1) The earliest time periods, the Paleozoic Era, most bony fish carried heavy armor in the form of thick scales covered with dense, shiny bone.

2) In the middle Periods, the Mesozoic, the armored fish became rarer and were replaced by fish with thin, flexible scales.

3) In the later Periods, the Cenozoic, thin-scaled fish took over in nearly all habitats.

4) Today, the old-fashioned thick scales persist only in a few fresh-water fish like the gar.

5) Tails changed too. The oldest bony fish had shark-like tails, with the vertebral column bending upwards to support the top of the fin. Later fish had more complicated tail bones, braced by special flanges, and the base of the tail was more symmetrical.

6) Jaws in the earliest bony fish were stiff, like the jaws of crocodiles. Later fish developed jaw bones that could swing outwards and forwards.

Discovery of the Ice Age
As he traveled across Europe, Agassiz saw evidence of giant ice sheets that had covered the mountains and plains. According to Agassiz’s theory, New England too had been invaded by mile-high ice layers. Giant hairy elephants – woolly mammoths – had frolicked in the frigid habitats. At first,  scholars harrumphed at Agassiz’s idea of a Glacial Period.  But by the mid 1840’s the theory was proven beyond a reasonable doubt.

Boston 1846: Toast of the Town & the New Museum
Fish and glaciers made Agassiz the most famous scientist of his time. When he came to Boston in the 1846, his lectures were so successful that the New England intellectuals wouldn’t let him leave. Poets and politicians, rich merchants and artists all helped raise funds to get Agassiz a professorship at Harvard. He repaid the support by working tirelessly to build a grand laboratory of science and education at Harvard – the Museum of Comparative Zoology. Opened in the 1859,  the MCZ has been a leader in fossil studies ever since.

Design in Nature
Agassiz’s interests spread beyond fish and glaciers. He sought the Plan of Creation, the key to understanding all of Nature. Was it  Evolution? No. Agassiz rejected any notion that natural processes somehow had transformed one species into another. He was a fierce exponent of the theory of Serial Creation: every species of fossil creature was created to fill its ecological role in its special geological time zone.

Darwin and Agassiz
Though he fought Darwin’s theories for his whole life, Agassiz’s work in fact provided support for the new views of evolution. The long trends in fish fins and scales were best explained by Natural Selection. Agassiz’s best students at Harvard went on to become strong supporters of Darwinism.  Endowed faculty positions were established in Agassiz’s name.  Agassiz Professorships were given to Alfred Sherwood Romer, the greatest Darwinian  paleontologist of the 20 century, and to Stephen Jay Gould, the most eloquent defender of Darwin in the last thirty years.

Don’t miss Archaeopteryx: Icon of Evolution, currently on display at HMNS. To read more about Agassiz and Darwin, check out my earlier blog.