Skull in Underwater Cave May Be Earliest Trace of First Americans

PET/GUE Divers descend into the abyss at Hoyo Negro.

Photo by Daniel Riordan-Araujo

By Fabio Esteban Amador

From http://blogs.nationalgeographic.com/

Explorers have discovered what might be the oldest evidence of humans in the Americas.

Alex Alvarez, Franco Attolini, and Alberto (Beto) Nava are members of PET (Projecto Espeleológico de Tulum), an organization that specializes in the exploration and survey of underwater caves on the Yucatan Peninsula in Mexico.

Alex, Franco and Beto have surveyed tens of thousands of feet of mazelike cave passages in the state of Quintana Roo. The team's relatively recent explorations of a large pit named Hoyo Negro (Black Hole, in Spanish), deep within a flooded cave, resulted in their breathtaking and once-in-a-lifetime discovery of the remains of an Ice Age mastodon and a human skull at the very bottom of the black abyss.

After trekking through the jungle, carrying multiple scuba cylinders, and traveling thousands of feet inside the Aktun-Hu cave system, PET/GUE Member Alex Alvarez discovered a human skull.

Photo by Daniel Riordan-Araujo 

Beto recalls the amazing day of the discovery of Hoyo Negro.

"We started the exploration while following the main tunnel and progressed relatively fast by using scooters to cover more terrain.

"After about 1,500 feet [450 meters] we began to see the light of another entrance, so we headed towards it and surfaced.

"After taking a moment to chat and laugh about what a great dive we were having, we dropped down to continue the work.

"After about 400 feet [120 meters] the tunnel narrowed to form a circular shape, almost like a huge cement pipe. I made one tie-off and, while waiting for Franco to complete his surveying effort, I took a good look at the strangely shaped tunnel.

"All I could see was the whiteness of the cave walls along the sides, and beyond that it was all black. I thought to myself that this is either the largest tunnel I have seen or there is something unusual at the end of it.

"After Franco caught up, we continued for another 200 feet [60 meters] and eventually reached the end of the tube-shaped tunnel. To our surprise the floor disappeared and all we could see was blackness in all directions. It felt like we had reached a big drop-off or the edge of a canyon wall.

"We tried to slow down our heart rates as we were not really sure of what to do next."

The Aktun-Hu cave system, where Hoyo Negro is located, is completely filled with water and is fully decorated with speleothems, like the Double Column formation shown in this photo.

Photo by Daniel Riordan-Araujo

Where is Hoyo Negro?

Hoyo Negro was reached by the PET team after the divers travelled more than 4,000 feet [1,200 meters] through underwater passages using underwater propulsion vehicles, or scooters, which enabled them to cover long distances in the flooded cave system.

Once they reached the pit, they began to survey and document its dimensions. The pit is approximately 200 feet [60 meters] deep and 120 feet [36 meters] in diameter and is located inside the Aktun-Hu cave system in the state of Quintana Roo, Mexico.

Submerged cave systems in Quintana Roo have been systematically surveyed and mapped by teams of highly specialized divers. The PET team is affiliated with Global Underwater Explorers, as is the Mexico Cave Exploration Project.

"The immense size of Hoyo Negro is difficult to comprehend. Once you enter the pit you cannot see the floor below, and all that can be seen in front of you is a black void -- an inviting entrance to the abyss, " recalls Franco.

The team of explorers touched bottom at 197 feet [57 meters], where they made their incredible discovery.

How Did the Tunnels Form?

The Yucatan Peninsula's geology is almost entirely limestone -- a karstic shelf that is easily dissolved by rainwater, forming caves and sinkholes.

Approximately 12,000 years ago, at the end of the Pleistocene epoch, Earth experienced great climatic changes. The melting of the ice caps caused a dramatic rise in global sea levels, which flooded low lying coastal landscapes and cave systems. Many of the subterranean spaces that once provided people and animals with water and shelter became inundated and lost until the advent of cave diving.

PET/GUE Diver Alex Alvarez looks at the remains of an extinct mastodon at the base of Hoyo Negro.

Photo by Daniel Riordan-Araujo

Ironically, the Yucatan Peninsula does not have any major rivers or lakes; however, there are many underground rivers and water-filled caves or sinkholes known as cenotes (a Spanish word derived from the Maya dzonot).

What Was Found at the Bottom of the Black Hole?

While the team of explorers conducted various dives for the purpose of mapping and surveying of this newly discovered pit, they noticed some peculiar bones sitting on the bottom. They first came across several megafauna remains and what was clearly a mastodon bone, while subsequent dives proved even more exciting when they spotted a human skull resting upside down with other nearby remains at about 140 feet [43 meters] depth.

"I was searching for more of the mastodon remains, when I saw what looked like a human skull. I had thought we already had a great discovery after finding the remains of several Pleistocene animals...but finding a human skull was totally amazing for us. All of our efforts... walking through the jungle, carrying all the gear, securing the helium required to do such a deep dive, laying thousands of feet of exploration line... paid off at that moment. This is the Holy Grail of underwater cave exploration," Alex said.

"This is the Holy Grail of underwater cave exploration."

Soon after the discovery, the team contacted Guillermo de Anda, an archaeologist from the University of Yucatan in Merida (UADY) who has also been documenting Pleistocene megafauna sites and who helped in the identification of the Hoyo Negro discovery.

"The findings of Hoyo Negro are a once-in-a-lifetime discovery. The skull looks pre-Maya, which could make it one of the oldest set of human remains in the area. Gaining an understanding of how this human and these animals entered the site will reveal an immense amount of knowledge from that time. Therefore, protecting and learning the secrets of Hoyo Negro should be one of the main priorities for the archaeologists in the region," Guillermo told News Watch in an interview.

PET/GUE Diver Franco Attolini places a scale and directional marker near an ancient human skull as part of the team's recent exploration efforts in the Yucatan Peninsula underwater caves.

Photo by Daniel Riordan-Araujo

The PET team formally announced the discovery at Hoyo Negro to Pilar Luna Erreguerena, Director of Underwater Archaeology for Mexico's National Institute for Archaeology and History (INAH). Pilar is the founder of underwater archaeology in Latin America and has been instrumental in protecting Mexico's submerged cultural heritage.

"This discovery is extremely important and confirms the cultural diversity and richness that can be found in the Yucatan Peninsula," said Pilar Luna. "INAH's division of underwater archaeology is preparing a multidisciplinary project together with discoverers of the site. This team work will allow us to scientifically recover the data and the evidence in its own context, so that experts may really get to know the true value of this discovery and turn it into a deeper knowledge or understanding of the prehistoric era in this part of Mexico."

At present, the entrance to the site is limited to INAH's research team since they are responsible for maintaining the integrity of the site.

Studies in the Tulum area, similar to those currently being planned for Hoyo Negro, were accomplished for the very first time by Pilar Luna's collaborators, namely Arturo González, Carmen Rojas, Octavio Del Río, Eugenio Aceves, and Jerónimo Avilés, with the support of Adriana Velázquez, Director of Centro INAH Quintana Roo.

GUE and INAH divers participate in a Nautical Archaeology Society training course in Tulum.

Photo by Olmo Torres Talamante

What is the Significance of the Discovery of Hoyo Negro?

The human found with the megafauna remains in Hoyo Negro could represent the oldest evidence of humans yet discovered in the Americas.

Archaeological and genetic data have long supported a northeast Asia origin for the populations that first settled North and South America. The so-called "First Americans" or Paleoindian peoples likely entered into these new lands sometime between 15,000 and 20,000 years ago.

Although a number of early archaeological sites have been excavated, only few sets of Paleoindian remains have been found. A detailed analysis of the human skeletal remains from Hoyo Negro can help us to better understand who these First Americans were and when they arrived here, which is one of the greatest mysteries in American archaeology.

Radiometric dating of the human bones from Hoyo Negro will have to wait for now, but its location within the cave, and its position relative to the mastodon remains, are suggestive of its antiquity. 

PET/GUE Divers exit from Hoyo Negro after a long documentation dive where they collected photos and videos of prehistoric remains.

Photo by Daniel Riordan-Araujo

Waitt Institute archaeologist and New World cave expert, Dominique Rissolo, offers a compelling argument for the importance of this site and similar discoveries. "The cenotes of Quintana Roo, Mexico, have emerged as one of the most promising frontiers for Paleoindian studies in the Americas.

"Recent discoveries of human remains deep within the region's flooded caverns, as well the bones of mastodons and other extinct species of Pleistocene megafauna, offer an extraordinarily rare glimpse into a period that witnessed the peopling of the New World.

"During the Late Pleistocene, these caves were dry. The first people to occupy what is now the Caribbean coast of Mexico wandered into these caves, where some ultimately met their demise.

"As the last glacial maximum came to end, the melting of the polar ice caps and continental ice sheets raised sea levels worldwide. The caves of the Yucatan Peninsula filled with water and the First Americans were hidden for millennia -- only to be discovered by underwater cave explorers

"It is within these dark reaches that cave explorers are discovering and documenting the oldest human skeletons yet found in the Western Hemisphere," Rissolo said.

Future Research at Hoyo Negro

In the summer of 2010, Pilar Luna organized a Nautical Archaeology Society training course for the Hoyo Negro team. The course, which was funded by National GeographicMagazine thanks to Chris Sloan, a magazine editor, covered the essentials of underwater archaeological site recording.

In collaboration with INAH, the team hopes to continue their exploration of Hoyo Negro and to thoroughly document the findings at the site.

Perhaps this is a turning point in scientific exploration in the region, where successful research will depend upon the knowledge and experience of a multidisciplinary team that includes underwater archaeologists, geologists, and paleontologists working side by side with highly skilled divers.

The National Geographic/Waitt Grants Program has funded similar research in the past by supporting GUE diver, Sam Meacham, in his cave exploration and water conservation work in Quintana Roo.

National Geographic has been active in featuring similar discoveries made by cave divers on the Yucatan peninsula. In 2008 National Geographic Daily News published the discovery of the Eve of Naharon, a female skeleton dated to 13,600 years old, which was also found in an underwater cave in Quintana Roo. (Oldest Skeleton in Americas Found in Underwater Cave? )

More recently in 2010, National Geographic Daily News published an article on the Young Man of Chan Hol, a possible ritual burial from 10,000 years ago. (Undersea Cave Yields One of Oldest Skeletons in Americas) 

In addition to the latest extraordinary expedition and amazing discovery, Robbie Schmittner connected the Aktun-Hu cave system (where Hoyo Negro is located) to theSac Actun cave system. Together they may now represent the longest underwater cave system in the world.

Future investigations in Hoyo Negro will no doubt reveal new clues about the peopling of the New World.

Evolution of Video Games

From: http://kokugamer.com/2010/08/03/info-graph-evolution-of-gaming/

Source [Online Schools.org]

Evolution of Cars by Country [PIC]

First genetic link between reptile and human heart evolution

September 2nd, 2009

Image: Wikimedia Commons

Scientists at the Gladstone Institute of Cardiovascular Disease have traced the evolution of the four-chambered human heart to a common genetic factor linked to the development of hearts in turtles and other reptiles.

The research, published in the September 3 issue of the journal Nature, shows how a specific protein that turns on genes is involved in heart formation in turtles, lizards and humans.

"This is the first genetic link to the evolution of two, rather than one, pumping chamber in the heart, which is a key event in the evolution of becoming warm-blooded," said Gladstone investigator Benoit Bruneau, PhD, who led the study. "The gene involved, Tbx5, is also implicated in human congenital heart disease, so our results also bring insight into human disease."

From an evolutionary standpoint, the reptiles occupy a critical point in heart evolution.

While bird and mammalian hearts have four chambers, frogs and other amphibians have three. "How did hearts evolve from three to four chambers?" Bruneau said. "The different reptiles offer a sort of continuum from three to four chambers. By examining them, we learned a lot about how the human heart chambers normally form."

He explained that with four chambers—two atria and two ventricles—humans and all other mammals have completely separate blood flows to the lungs and to the rest of the body, which is essential for us to be warm-blooded.

Enlarge

Embryo hearts show evolution of the heart from a three-chambered in frogs to a four-chambered in mammals. Credit: Zina Deretsky, National Science Foundation after Benoit Brueau, the Gladstone Institute of Cardiovascular Disease

When it comes to reptiles, such as turtles and lizards, there is debate about whether they have one or two ventricles, which are the pumping chambers. "The main question for us to understand the evolution of the heart was to identify the true nature of these early reptile ventricles and to figure out what controls the separation of the heart into left and right sides," said Dr. Bruneau.

To better understand reptile heart evolution, Dr. Bruneau's team used modern molecular genetics to examine Tbx5. Mutations in the human gene that encodes Tbx5 result in congenital heart disease and, in particular, defects in the ventricular septum, the muscular wall that separates the ventricle into two sections. Tbx5 is a transcription factor, a protein that turns other genes on or off. In humans and other mammals, Tbx5 levels are high in the left ventricle and low in the right. The boundary of high and low levels is right where the septum forms to divide the ventricle into two parts. "Based on these observations," said Dr. Bruneau, "we thought Tbx5 was a good candidate as a key player in the evolution of septation."

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The team looked at Tbx5 distribution in the turtle and the green anole lizard. During the early stages of heart formation in both reptiles, Tbx5 activity is found throughout the embryonic ventricular chamber. In the lizard, which forms only one ventricle, this pattern stays the same as the heart develops. However, in the turtle, which has a primitive septum that partially separates the ventricles into left and right sides, distribution of Tbx5 is later gradually restricted to the area of the left ventricle, resulting in a left-right gradient of Tbx5 activity. This meant that the gradient of Tbx5 forms later and less sharply in the turtle than in species with a clear septum, such as mammals, providing a tantalizing clue about how septation evolved.

Enlarge

The three-chambered frog heart mixes oxygenated and deoxygenated blood in the ventricle. Therefore, the body never receives fully oxygen-rich blood. In turtles, where a septum begins to form and separate the ventricles, the body receives slightly richer blood in oxygen. It is only in the warm-blooded model, in birds and mammals, that the two circulatory systems become fully separate sending low-pressure pumping to the lungs, and a high-pressure flow of blood to the rest of the body. In this model, the animal's muscles receive fully oxygenated blood. Credit: Credit: Zina Deretsky, National Science Foundation

They then wanted to determine whether Tbx5 was really a main regulator of septation or merely a bystander. Mice were genetically engineered to express Tbx5 at a moderate level throughout the developing heart, just like in turtle hearts. By mimicking the turtle pattern, mouse hearts now resembled turtle hearts. The offspring from these mice died young and had only a single ventricle. This striking result conclusively showed that a sharp line delineating an area of high level of Tbx5 is critical to induce formation of a septum between the two ventricles.

"This really nailed the importance of Tbx5 in patterning the heart to allow septation to occur," said Dr. Bruneau.

During evolution, new genetic regulatory elements evolved to tell the Tbx5 gene to form a sharp boundary of Tbx5 expression. This resulted in two ventricles. Researchers will now work to identify those genetic regulatory mechanisms during the evolution of reptiles. The work also has important implications for the understanding of congenital heart defects, which are the most common human birth defect, occurring in one out of every one hundred births worldwide. Humans born with only one pumping chamber, resembling frog hearts, suffer the highest mortality and require extensive surgery as newborns.

"Our study provides exciting new insights into the evolution of the heart, which had not been examined in over 100 years," Dr. Bruneau explained. "In a larger context, it provides good support for the concept that changes in the expression levels of various regulatory molecules are important in evolution. From these studies we also hope to understand further how defects in septation occur in humans with congenital heart disease."

Source: Gladstone Institutes (news : web)

New Bird Evolves Faster than Any Other

Written by Jake Richardson

A bird recently discovered in the Solomon Islands is a member of the White Eyes (Zosteropidae) family that evolves more rapidly than any other bird.

The newly discovered species has been named Vanikoro White Eye. It was found on the tiny island of Ranongga, and is thought to only live there.

Genetic research has shown what two scientists suspected 80 years ago: that there are different species of White Eyes on separate islands in the Solomons. Sometimes the islands are only 2-3 kilometers apart and yet they have their own species of White Eye. One of the researchers, Rob Moyle from the University of Kansas said this of their initial investigation, “As we started to compile the data, we were shocked…White-eye species from across the family’s range had strikingly similar gene sequences, indicating a recent origin and incredibly rapid diversification.”

Moyle collaborated with Dr. Chris Filardi and Dr. Jared Diamond. Diamond actually had worked with the original scientist (Ernest Mayr) who first noted the difference between the White Eyes when visting the Solomons decades ago. DNA analysis of many White Eyes species by Filardi and his team showed that they can generate about 2-3 new species every million years.

Filardi commented on the research, “There’s something special about these birds. White eyes quickly diverge into new species across water gaps as narrow as a couple of kilometers- gaps that other birds easily bridge to maintain gene flow.” In the Solomons alone there are thirteen species of White Eyes. Because of its rapid capacity for diversification, some call White Eyes the Great Speciator. Over 100 species of the bird are distributed throughout the world.

Animals thought to have a higher rate of speciation are the Cichlid fish in Africa, and the Tuatara, a reptile that lived at the same time as some dinosaurs. Recently a baby Tuatara was found on mainland New Zealand.

(Author’s note:The Jared Diamond referenced here is also the Pulitzer prize-winning author of Guns, Germs, and Steel).

Image Credits: 1. Close-up: Dr. Chris Filardi, American Musuem of Natural History
2. Tri-species illustration, BirdLife International 3. Vanikoro White Eyes in Tree, Dr. Guy Dutson

Pink Iguana That Darwin Missed Holds Evolutionary Surprise

By Alexis Madrigal

For iguanas, it turns out that it's not easy being pink, either.

Biologists report that a rare type of pink iguana found on a single volcano in the Galapagos Islands is a genetically-distinct species from its green cousins — and that it's probably critically endangered.

"This form, which we recognize as a good species, is very important because it carries substantial evolutionary legacy," the authors of a new paper in the journal Proceedings of the National Academy of Sciences wrote. "Thus far the rosada form is the only evidence of deep diversification along the Galapagos land iguana lineage."

Charles Darwin visited the Galapagos islands in 1835 but didn't make it to the northernmost volcano, Volcan Wolf, which is the lone habitat for these pink lizards. Later travelers and scholars also seem to have missed or failed to report the curiously striped creature until 1986 when some Galapagos National Park rangers spotted the animals. Still, no scientists had looked into whether they represented a distinct species until now.

What they found was surprising. Instead of being some slight variation on the Galapagos iguana theme, the pink lizards represent a distinct and early branch of the genetic tree. The genomic analysis of the species suggests that they broke from other iguanas about five million years ago, much deeper in history than most other Galapagos species, like Darwin's finches. In addition to the genetic differences, the pink iguanas also perform the characteristic mating ritual "head-bob" differently.

The iguana and other animals on Volcan Wolf are threatened by an "invasion of feral goats" that are devastating the area's natural flora.

In the interest of preserving this genetic diversity, the biologists wrote that "a conservation program aimed at evaluating the risk of extinction of this newly recognized species," should be initiated. They estimate that the iguana could already by termed "critically endangered."

Citation: "An overlooked pink species of land iguana in the Galapagos" by Gabriele Gentile, Anna Fabiani, Cruz Marquez, Howard L. Snell, Heidi M. Snell, Washington Tapia, and Valerio Sbordonia in the Proceedings of the National Academy of Sciences. DOI: 10.1073/pnas.0806339106

Top 10 Useless Limbs (and Other Vestigial Organs)

livescience.com — In Charles Darwin's On the Origin of Species (1859) and in his later works, he referred to several "vestiges" in human anatomy that were left over from the course of evolution.

10) The Wings on Flightless Birds

The Cassowary, the sexier, but less-well-known flightless bird.

In 1798, sixty years before Charles Darwin?s first book was published, a French anatomist, É´ienne Geoffroy St. Hilaire, traveled to Egypt with Napoleon where he witnessed and wrote about a flightless bird whose wings appeared useless for soaring. The bird that Hilaire described was an ostrich, but he described it as a "cassowary", a term used back then to describe various birds of ostrich-like appearance. Ostriches and cassowaries are among several birds that have wings that are vestigial. Besides the cassowary, other flightless birds with vestigial wings are the kiwi, and the kakapo (the only known flightless and nocturnal parrot), among others. In general, wings of a bird are considered complex structures that are specifically adapted for flight and those belonging to these flightless birds are no different. They are, anatomically, rudimentary wings, but they could never give these bulky birds flight. The wings are not completely useless, as they are used for balance during running and in flagging down the honeys during courtship displays.

9) Hind Leg Bones in Whales

Whale skeleton showing pelvis and thigh bones (see inset).

Biologists believe that for 100 million years the only vertebrates on Earth were water-dwelling creatures, with no arms or legs. At some point these ?fish? began to develop hips and legs and eventually were able to walk out of the water, giving the earth its first land lovers. Once the land-dwelling creatures evolved, there were some mammals that moved back into the water. Biologists estimate that this happened about 50 million years ago, and that this mammal was the ancestor of the modern whale. Despite the apparent uselessness, evolution left traces of hind legs behind, and these vestigial limbs can still be seen in the modern whale. There are many cases where whales have been found with rudimentary hind limbs in the wild, and have been found in baleen whales, humpback whales, and in many specimens of sperm whales. Most of these examples are of whales that had only leg bones, but there were some that included feet with complete digits. It was reported recently that whales and hippos were distantly related.

8) Erector Pili and Body Hair

When a rabbit is scared, its hair stands on end. When a human is scared, he or she calls the police.

The erector pili are smooth muscle fibers that give humans ?goose bumps.? If the erector pili are activated, the hairs that come out of the nearby follicles stand up and give an animal a larger appearance that might scare off potential enemies and a coat that is thicker and warmer. Humans, though, don?t have thick furs like their ancestors did, and our strategy for several thousand years has been to take the fur off other warm looking animals to stay warm. It?s ironic actually that an animal, sensing danger is near, would puff up its coat to look scarier, but the human hunter would see the puffier coat as a warm prize, leaving the thinner haired weaker looking animals alone. Of course, some body hair is helpful to humans; eye brows can keep sweat out of the eyes and facial hair might influence a woman?s choice of sexual partner. All the rest of that hair, though, is essentially useless.

7) The Human Tailbone (Coccyx)

The human tailbone doesn't do much, but really hurts if you land on it.

These fused vertebrae are the only vestiges that are left of the tail that other mammals still use for balance, communication, and in some primates, as a prehensile limb. As our ancestors were learning to walk upright, their tail became useless, and it slowly disappeared. It has been suggested that the coccyx helps to anchor minor muscles and may support pelvic organs. However, there have been many well documented medical cases where the tailbone has been surgically removed with little or no adverse effects. There have been documented cases of infants born with tails, an extended version of the tailbone that is composed of extra vertebrae. There are no adverse health effects of such a tail, unless perhaps the child was born in the Dark Ages. In that case, the child and the mother, now considered witches, would?ve been killed instantly.

6) The Blind Fish Astyanax Mexicanus

Astyanax Mexicanus: growing up in the wrong neighborhood.

In an experiment designed by nature, the species of fish known as Astyanax mexicanus, dwelling in caves deep underground off the coast of Mexico, cannot see. The pale fish has eyes, but as it is developing in the egg, the eyes begin to degenerate, and the fish is born with a collapsed remnant of an eye covered by flap of skin. These vestigial eyes probably formed after hundreds or even thousands of years of living in total darkness. As for the experiment, a control is needed; and luckily for us, fish of the same species live right above, near the surface, where there is plenty of light, and these fish have fully functioning eyes. To test if the eyes of the blind mexicanus could function if given the right environment, scientists removed the lens from the eye of the surface-dwelling fish and implanted it into the eye of the blind fish. It was observed that within eight days an eye started to develop beneath the skin, and after two months the fish had developed a large functioning eye with a pupil, cornea, and iris. The fish were blind, but now they see.

5) Wisdom Teeth in Humans

They need regular brushing.

With all of the pain, time, and money that are put into dealing with wisdom teeth, humans have become just a little more than tired of these remnants from their large jawed ancestors. But regardless of how much they are despised, the wisdom teeth remain, and force their way into mouths regardless of the pain inflicted. There are two possible reasons why the wisdom teeth have become vestigial. The first is that the human jaw has become smaller than its ancestors? and the wisdom teeth are trying to grow into a jaw that is much too small. The second reason may have to do with dental hygiene. A few thousand years ago, it might be common for an 18 year old man to have lost several, probably most, of his teeth, and the incoming wisdom teeth would prove useful. Now that humans brush their teeth twice a day, it?s possible to keep one?s teeth for a lifetime. The drawback is that the wisdom teeth still want to come in, and when they do, they usually need to be extracted to prevent any serious pain.

4) The Sexual Organs of Dandelions

Send in the clones ...

Dandelions, like all flowers, have the proper organs (stamen and pistil) necessary for sexual reproduction, but do not use them. Dandelions reproduce without fertilization; they basically clone themselves, and they are quite successful at it. Look at any lawn for the proof. If dandelions were to revert to sexual reproduction, they might not retain whatever traits they have that allow them to be pests to gardeners everywhere. If flowers can begin reproducing in this manner, does that mean animals, even humans could too? Asexual reproduction can be a good strategy in an environment that is constant if a species is well suited to those conditions. It doesn?t take a scientist to figure out that humans wouldn?t last long if the condition set forth was no sexual contact with others. Therefore, the human sexual organs are probably in no danger of becoming vestigial.

3) Fake Sex in Virgin Whiptail Lizards (Vestigial Behavior)

Feminist lizards take the male out of the picture.

Only females exist in several species of the lizards of the genus Cnemidophorus, which might seem like a problem when it comes time to propagate the species. The females don?t need the males though, they reproduce by parthenogenesis, a form of reproduction in which an unfertilized egg develops into a new individual. So basically, the females don?t need the males; they just produce clones of themselves as a form of reproduction. Despite the fact that it is unnecessary and futile to attempt copulation with each other, the lizards still like to try, and occasionally one of the females will start to ?act like a male? by attempting to copulate with another female. The lizards evolved from a sexual species and the behavior to copulate like a male -- to engage in fake sex -- is a vestigial behavior; that is, a behavior present in a species, but is expressed in an imperfect form, which in this case, is useless.

2) Male Breast Tissue and Nipples

Oh yeah, really handy those ...

The subject of male nipples is a sensitive, and maybe confusing, topic to many. Those who wish to invalidate evolutionary theory might pose the question, ?Was man descended from woman?? The answer, of course, is no. Both men and women have nipples because in early stages of fetal development, an unborn child is effectively sexless. Nipples are present in both males and females; it is only in a later stage of fetal development that testosterone causes sex differentiation in a fetus. All mammals, male and female, have mammary glands. Male nipples are vestigial; they may perform a small role in sexual stimulation and a small number of men have been able to lactate. However, they are not fully functional and, because cancer can grow in male or female breast tissue, the tissue can be dangerous.

1) The Human Appendix

Leonardo da Vinci?s sketch of the intestines that included the appendix.

In plant-eating vertebrates, the appendix is much larger and its main function is to help digest a largely herbivorous diet. The human appendix is a small pouch attached to the large intestine where it joins the small intestine and does not directly assist digestion. Biologists believe it is a vestigial organ left behind from a plant-eating ancestor. Interestingly, it has been noted by paleontologist Alfred Sherwood Romer in his text The Vertebrate Body (1949) that the major importance of the appendix ?would appear to be financial support of the surgical profession,? referring to, of course, the large number of appendectomies performed annually. In 2000, in fact, there were nearly 300,000 appendectomies performed in the United States, and 371 deaths from appendicitis. Any secondary function that the appendix might perform certainly is not missed in those who had it removed before it might have ruptured.

Mysterious DNA Found to Survive Eons of Evolution

By Clara Moskowitz, LiveScience Staff Writer

The mystery DNA spippets are about 300 times less likely than other regions of the genome to be lost during the course of mammalian evolution. Credit: Dreamstime

Scientists have discovered mystery snippets of mammal DNA that have survived eons of evolution and yet have no apparent purpose. The finding reveals just how much we don't know about the secrets hidden in our genome and that of other animals.

Most genes change throughout evolution via mutations; useless ones eventually get weeded out of the population while the helpful modifications take hold. However, about 500 regions of our DNA — the body's instruction code made up of base pairs of molecules — have apparently remained intact throughout the history of mammalian evolution, or the past 80 million to 100 million years, basically free of mutations.

"Mutations are introduced into these regions just as they are everywhere else, but they're swept out of the genome much more quickly," said researcher Gill Bejerano, professor of developmental biology and computer science at Stanford University. "These regions seem to be under intense purifying selection — almost no mutations take hold permanently."

And what's more, many of those sequences do not appear to code for any obvious function, or phenotype, in the body. Researchers suspect they do serve an important purpose, but have yet to figure out exactly what that purpose is. (These sequences are not the same as most non-coding or "junk" DNA, for which no function has been identified, because those sections are not so well-preserved.)

Ultraconserved regions

The researchers call these mystery snippets "ultraconserved regions," and found that they are about 300 times less likely than other regions of the genome to be lost during the course of mammalian evolution. Bejerano and his graduate student Cory McLean detailed the finding in the journal Genome Research.

The fact that these segments haven't been weeded out by natural selection implies that they serve an important function in mammals. Yet mice in the lab bred to lack four of these DNA strands appear healthy and don't seem to be missing any vital genes.

Wondering if the odd results were simply some fault of the lab experiment, and perhaps the mice really weren't as well off as they seemed, the researchers investigated whether any other mammals were also blithely living without these regions.

Amazingly, they found that was not the case. The researchers compared ultraconserved sequences of at least 100 base pairs shared by humans, macaques and dogs with the DNA of rats and mice. They found that less than one-tenth of 1 percent of the segments shared among the primates and dogs were missing in the rodents. In contrast, about 25 percent of regular, not ultraconserved, regions in the first group were absent in the mice and rats.

"What's striking about this research is that [the regions] really are almost never lost," Bejerano told LiveScience. "You're asking if a species can live without these regions, and the resounding answer from our paper is that they seem to have an effect that is strong enough that evolution would weed [individuals without the regions] out of an evolving population."

Potential purposes

Scientists have some guesses about what these strange segments might be used for. Perhaps these DNA strands actually code for multiple layers of information, Bejerano suggested. In that case, each layer could be redundant, with other segments serving the same purpose in other contexts, but together they provide a vital backup system.

Or, they could be crucially important, but only at specific times in a species' history.

"Imagine that these regions somehow protect you from a disease that only strikes the population every once in a while," Bejerano said. "Once every 10,000 years you have this cleansing event, and only those with the region would actually stick around. That's one guess."

Mysterious DNA

For all the major advances in genome science in the last decades, there are still many basic questions left to be answered.

For one thing, though researchers have made strides in understanding what many genes do, there are many more areas of DNA that remain baffling.

"If you pick a particular region in the genome at random and ask me, 'What does this region do?' there is a very high likelihood that I would tell you, 'I don’t know,'" Bejerano said in a phone interview. "That makes for a lot of mysteries that are still out there."

In addition to particular sequences of DNA that puzzle scientists, there are many basic questions about the workings of DNA for which answers have so far eluded researchers.

"We have very good guesses, but how the genome does its thing is by and large yet to be revealed," Bejerano said. "It's exactly the same in every one of our cells, but each cell behaves very differently. There's a lot more we have to understand in the relationship between genomics and developmental biology."

The research was supported by a Stanford Bio-X graduate fellowship and an Edward Mallinckrodt, Jr. Foundation junior faculty grant. Bejerano is a Sloan research fellow and a Searle scholar