Transcript Dwarves
The Biology of Monsters
• Many of the creatures found in myths and fairy tales have some basis in biological facts. Our forebears may have extrapolated and expanded on what they saw and heard about, but there was usually a kernel of truth underlying the myth.
• Here I have presented some biological information about several such phenomena: dwarves, cyclopses, werewolves, vampires, two-headed monsters, human animal hybrids.
• Please be aware that some of the images presented here are quite graphic.
• Also, please be a bit sensitive to the people born with various genetic conditions. They may appear strange, but they ar no less human than we are.
Dwarves
• “Dwarfs” is the more accepted spelling. JRR Tolkein has resurrected the plural form from Old English.
• A race of short people, perhaps miners and warriors. Similar to humans, equals of humans, but not really “us”.
Dwarf Images
• Or perhaps figures of fun: circus freaks, the Munchkins of
The Wizard of Oz
, the Oompa-Loompas of
Willy Wonka and the Chocolate Factory
.
• Good book:
The Munchkins of Oz
, by Stephen Cox, about the little people who played the Munchkins.
Achondroplasia
• • Achondroplasia is the most common form of dwarfism, 70% of all cases. Symptoms include a torso of normal length, with disproportionately short arms and legs. Other features are a large head with a high forehead, and a small, often turned-up nose. Achondroplasia is recognizable at birth. In many cases, the legs bow outward.
The major medical problem with dwarfism is “spinal stenosis”, in which the channel in the vertebrae that holds the spinal cord is too small. This results in compression of the nerves, with numbness and paralysis possible. The bad fit between large head and small spinal column also causes hydrocephalus (spinal fluid buildup crushing the brain) in some cases.
Biochemistry of Dwarfism
• • • • • • • Achondroplasia is caused by a gene mutation.
The gene is involved makes the protein “fibroblast growth factor receptor-3”. Fibroblasts are the cells that make skin, bones, and other connective tissues; fibroblasts make and secrete collagen, the protein that gives these tissues their structure.
A “growth factor” is a small molecule (a small protein) secreted by one cell that causes the cells around it to grow and multiply. The growth factor receptor is a protein on the surface of the fibroblast cells that acts as an antenna: it attracts and binds the matching growth factor molecules that approach it, then passes a signal along to the inside of the cell, telling it to grow and divide.
There are at least 22 different fibroblast growth factors in humans, with matching receptors. Different cell types use different signals.
The achondroplasia gene just happens to be very sensitive to mutation at one particular spot, for unknown reasons.
Genetics of Dwarfism
• • • • • Inherited as a dominant trait: those with 1 mutant (dwarf) gene and 1 normal gene show the condition. If both copies of the gene are mutant, the child invariably dies around the time of birth.
Most dwarves are born to normal parents: a random mutation occurred in one of the parents.
If a dwarf mates with a normal sized person, ½ of their children will be dwarf, ½ normal.
If 2 dwarves mate, ¼ will be normal, ½ will be dwarf, and ¼ will be “double dominants” who die at a very young age.
Because dwarves are heterozygotes: they have 1 normal copy of the gene and one mutant copy born. —the condition does not breed true. It is impossible to create a race of dwarves because they will inevitably have a significant number of normal size children
Cyclops
• The one-eyed monster of the
Odyssey
, who ate human flesh. The Cyclopes were a race of beings, children of Uranus and Gaea, brothers of Chronos (Saturn, Zeus’s father). In the Odyssey, the Cyclops Polyphemus lives a barbaric life in a cave, herding sheep, killing passers-by. The resourceful Odysseus gets him drunk on wine, then puts out his eye and escapes tied under a sheep. Also discussed in the play
The Cyclops
, by Euripedes, and in Hesiod.
Holoprosencephaly
• • • • Holoprosencephaly: failure of the forebrain to divide into 2 lobes during embryonic development. Many degrees of expression and severity, but the cyclopia form includes development of a single orbit where the nose normally is, and a nose that is either missing or present as a proboscis above the eye. Sometimes there is no eyeball, sometimes one, and sometimes two. Usually a single optic nerve leading to the undivided brain. Affects about 1 in 16,000 live births, but only rarely survive to birth, usually aborted in embryonic life (before 3 months gestation time). Survivors are severely mentally deficient.
Less severe cases have two eyes, but a single nostril and a flat nose. Even less severe: cleft lip.
Trisomy-13 (Patau Syndrome)
• • • • Normal humans have 2 copies of each chromosome, one from each parent.
Sometimes, there is an extra or missing chromosome. Three copies of a chromosome is called “trisomy”. The most common form of trisomy is trisomy-21, or Down Syndrome.
Patau Syndrome, 3 copies of chromosome 13, is quite rare: about 1 in 10,000 live births.
The standard symptoms of Patau syndrome include extreme cleft lip and palate, extra fingers and toes, and severe mental retardation. Average survival time after birth is less than 3 days. Oldest known case lived to age 21. The cyclops condition is an occasional symptom.
Cause of Patau Syndrome
• • • • • The presence of an extra chromosome is due to “non-disjunction”, the failure of chromosomes to properly separate during the formation of the sperm and egg cells.
Our body cells are all diploid: 2 copies of each chromosome. The gametes, the sperm and egg cells, must be haploid, one copy of each chromosome, so that when the sperm fertilizes the egg, the diploid condition is restored.
The special cell division process to convert a diploid body cell into a haploid gamete is called “meiosis”. During meiosis, the pairs of chromosomes line up in the center of the cell, then each pair gets separated into different cells. Non-disjunction occurs when both members of a pair go into the same cell. The rate of non-disjunction is greatly affected by the mother’s age.
Most embryos with extra or missing chromosomes are spontaneously aborted. Down and Patau syndromes are unusually viable.
Werewolves
• • • Lycanthropy, the belief that one is a wolf (or other wild animal) is a form of psychosis. Few scientists believe that it is actually possible to physically change from a human into a wolf.
King Nebuchadnezzar of Babylon, described in the Book of Daniel in the Bible, apparently had this belief. It is found in culture throughout the world, associated with the local carnivores: were-crocodiles, tigers, bears, and sharks have all been described. Accidental ingestion of hallucinogenic substances, such as ergot mold (on infected rye) may have contributed to some of these beliefs. More recent cases often involve more recent drugs. Psychosis is another major cause.
Lycanthropy
• • A case in 1977 described in the American Journal of Psychiatry (volume 134 number 10). Here is part of that description: “A 49 year-old married woman presented on an urgent basis for psychiatric evaluation because of delusions of being a wolf and "feeling like an animal with claws." She suffered from extreme apprehension and felt that she was no longer in control of her own fate: she said, "A voice was coming out of me." Throughout her 20-year marriage she experienced compulsive urges towards bestiality, lesbianism, and adultery.” A Google search easily finds numerous people who feel that they are werewolves, or at least animal trapped in human form. There is a whole movement called “furries”, in which the participants dress in animal costumes and do odd things.
Hypertrichosis
• • • • • Hypertrichosis univeralis: hair everywhere. People with this condition at least look like werewolves ought to look. Peter Gonzales, born in 1556 in the Canary Islands, lived in the court of Henry II of France. His 3 children (2 daughters and a son) and grandchild) also had hypertrichosis. They lived at Ambras castle in Austria; one form of hypertrichosis is called “Ambras syndrome”.
Stephan Bibrowsky, born in Poland in 18, exhibited as “Lionel the Lion-faced Man”. He worked for the Barnum and Bailey circus, using the story that when she was pregnant, his mother was attacked by a lion. He wore good clothes and held intelligent literary discussions with the people who came to see him, demonstrating that underneath the hair he was a normal man. There are several forms, and a lot of variation between individuals. Some geneticists consider this an example of an “atavism”, an ancestral trait that is no longer expressed in most people, but lies dormant in our genome.
Vampires They drink your blood, fear the sunlight, and associate with bats.
Count Dracula from Transylvania is the prototype.
The Real Dracula
• • • Dracula means “son of Dracul” in Romanian. Vlad, son of Dracul (Dracul means “dragon”), was a ruler in Transylvania, in Romania during the 1400’s. At that time, Romania was ruled by the Ottoman Turks. Vlad spent most of his time fighting the Turks and the Hungarians.
Vlad get his nickname “the Impaler” from his habit of impaling hundreds of victims on stakes, a very unpleasant and slow way to die. He occasionally ate bread that had been soaked in his victims’ blood. Dracula had a modern counterpart in Nicolae Ceausescu, the Communist ruler of Romania from 1967 to 1989. Ceausescu was a paranoid who ran a very unpleasant Soviet-style country: no freedom of expression, starvation due to the export of most food, birth control forbidden, and a personality cult revolving around himself and his wife. In 1989 Ceausescu and his wife faced a firing squad.
Vampire Bats
• Vampire bats, which drink the blood from cattle and other large animals, are found in Central and South America. They are small: 8 inch wingspan. Their saliva contains an enzyme that inhibits blood clotting and also acts as an anaesthetic. They make several small cuts in their victim’s skin, then lap up the blood.
• Vampire loonies: Johnny Blood ran for Parliament in Banbury,England on the Monster Raving Loony Party ticket. He campaigned as a vampire, with the promise that he would eat his constituents last. He got 9 votes.
Porphyria
• • • • Porphyria is a group of 8 metabolic diseases that stem from a buildup of precursors for heme. Heme is the small molecule that holds the iron atoms in hemoglobin. Hemoglobin is a protein that carries oxygen in the blood, and it is red due to its iron atoms. Heme must be synthesized in the liver, building up the molecule from precursors in a series of steps. In some forms of porphyria the skin burns and blisters on exposure to sunlight. The excess heme precursors are excreted in the urine, which often turns red or dark on exposure to the air. Lack of heme means pale skin due to anemia. Drinking blood was considered to be a cure in olden times. Modern treatment includes injection of heme directly into the blood. Psychosis and dementia are also common symptoms.
Porphyria Genetics
• • • Most types are inherited as recessive mutations. This means that only those who inherit two bad copies of the gene, one from each parent, will get it. Because this is a relatively rare disease, the easiest way to inherit two mutant genes is through inbreeding, the mating of close blood relatives. For example, first cousins have one set of common grandparents. If one of these grandparents carries a porphyria gene, each cousin has a ¼ chance of also carrying that gene. Then, their children have a ¼ chance of inheriting the porphyria gene from both parents and getting the disease. Recessive genetic diseases are fairly common in small inbred populations, such as royal families.
King George III (and his grandmother Mary Queen of Scots) had this disease. The resulting psychosis may well have affected the course of the American Revolution. Movie:”The Madness of King George”.
• • •
Cerberus and Two-Headed Monsters
Cerberus —the 3 headed dog who guarded the road to the Underworld, not allowing the inhabitants to return to Earth. Hercules “borrowed” him for a while as one of his twelve labors, and the great singer Orpheus escaped from the Underworld with his wife Eurydice by lulling Cerberus to sleep with a song. Unfortunately, Orpheus looked back at his wife before reaching the Earth, and she was forced to stay in the Underworld.
Janus, the 2-faced god of doors and beginnings. Fearsome monsters with 2 heads coming from one body.
Twinning
• • • • • All such creatures are the result of twin conceptions and births.
Two basic types of twins: fraternal (or dizygotic) and identical (of monozygotic). Fraternal twins are the result of 2 eggs fertilized by 2 sperm: siblings who just happen to share a womb. They are often of opposite sexes. Sometimes they even have different fathers. In most cases, human females release only a single egg, but occasionally 2 or more are released, giving rise to fraternal twins. Higher multiple births, especially under the influence of fertility drugs, are usually fraternal. “Dizygotic” means 2 zygotes (fertilized eggs).
The fetus is surrounded by 2 membranes, the chorion and the amnion. In fraternal twins, both membranes are separate. Sometimes the placentas fuse.
Identical Twins
• • • • • Identical twins (monozygotic) are the result of 1 egg fertilized by 1 sperm. After fertilization, the fertilized egg (zygote) divides into 2 cells, then 4, then 8, etc. For unknown reasons, sometimes embryos split into 2 or more pieces. These become identical twins. “Monozygotic” means that they started with 1 fertilized egg. If the split is early enough (before 4 days), the twins develop within separate outer and inner membranes (chorion and amnion). This is the usual situation.
A somewhat later split, between 4 and 8 days, results in twins that develop within a single chorion, but separate amnions. A still later split, between 8 and 12 days, causes development within a single inner membrane. Because they share a blood supply, sometimes one twin will get too much blood and the other not enough: this is “twin to twin transfusion syndrome”, and it can kill either or both of the twins. Still later splits, after 12 days, result in conjoined twins.
Limits on Twinning
• • • The single cell of the fertilized egg develops into every cell in the body. It is “totipotent”. This works up to the 4 cell stage in humans: each cell in a 4 cell embryo can develop into an entire human being. The Dionne quintuplets (born 1934) were apparently identical, so this works even slightly beyond the 4 cell stage. However, cells that become separated after the 4 cell stage embryo are unable to develop into complete individuals. They have lost the property of “totipotency”, the ability to develop into any type of cell.
Conjoined Twins
• • If embryonic cells become partially detached from each other, conjoined twins can result. Used to be called “Siamese twins”, after Chang and Eng Bunker, who were born in Thailand (called Siam in those days) in 1811. Their parents were Chinese, and in Siam they were known as the “Chinese twins”. They were discovered by an English merchant who got permission from their mother and the Siamese government to exhibit them. Later they toured with P.T. Barnum’s circus. Eventually they left show business, and settled down as farmers in North Carolina, married 2 sisters and had several children apiece. None of the children were twins of any sort, although 2 of their granddaughters produced twins. They died within a few hours of each other at age 63. They were joined by a thick ligament at the abdomen, and they could easily have been separated during their lives.
More Conjoined Twins
• There are wide variations in the degree of shared tissue and the point of attachment, all based on when, where, and how completely the embryonic cells separated. • Most common form: joined at the thorax with a shared heart. • 75% of such cases are stillborn or die within 24 hours of birth.
Asymmetric Conjoined Twins
• In most cases the two individuals are symmetrical, but sometimes one is only partially formed and the other is complete. This is called “parasitic twins”; in many cases the parastiic twin lacks a brain and a heart, conditions incompatible with life. Sometimes one twin inside the other (often incomplete: called fetus in fetu.
Two-headed Conjoined Twins • The “dicephalous” type of conjoined twins: 2 heads and necks on a single body —is very rare.
• A Google search turned up pictures of a 2 headed moose, several two-headed snakes, squirrel, tortoise, and toad.
Chimera, Sphinx, and Manticore
• • • Chimera —foreparts of a lion, hindparts of a goat, tail of serpent, breathed fire. Killed by Bellerophon with the aid of the winged horse Pegasus. In one version of the myth, Bellerophon thrust a block of lead at the Chimera, and her fiery breath melted the lead, which smothered her. The Sphinx had the head of a human female, body of a lion, and wings of an eagle. The most famous Sphinx figures in the myth of Oedipus. The Sphinx lived near Thebes, and devoured all who couldn’t answer her riddle, “What goes on 4 legs in the morning, 2 legs in midday, and 3 legs in the evening?” Oedipus answered that Man crawls on all fours as a baby, walks on 2 legs as an adult, and then hobbles with a staff in old age. The Sphinx became distraught at this answer and threw herself off a cliff. Oedipus was made king of Thebes, were he unknowingly killed his father and married his mother. This event lead to a great deal of unpleasantness in Oedipus’ subsequent life. Manticore: face of a man, body of a lion, tail of a scorpion.
Interspecies Hybrids
• • Why can’t different species produce offspring? Some sterile offspring among close species: mule = horse x donkey, also lion x tiger, zebra x horse, zebra x donkey, cow x buffalo, coyote x wolf, plus many others. Sheep x goat usually results in stillborn, but occasionally born alive. But this gets down to the definition of a species; inability to produce a fertile offspring. And, in evolutionary terms, when mating between two creatures results in no offspring or infertile offspring, “reproductive isolation”, various mechanisms evolve to prevent further mating. Some mechanisms are behavioral or appearance: not attractive to one another. Others involve fertilization: the sperm of one species don’t recognize the eggs of another species. Or embryonic development may not occur properly: signals between cells not sent or received properly, or genes don’t interact smoothly. Or the hybrid creature might be rejected by its mother by not smelling or looking right. Many possibilities. The division between species is very fundamental.
Human Mosaics and Chimeras
• • • • • A “mosaic” is a person having cells with two different genetic constitutions. Normally, all the cells in our bodies have the same genetic makeup: the same genes and chromosomes. What makes a liver cell different from a muscle cell, for instance, is difference in which genes are being expressed and not expressed. Many genes only function in one type of cell.
Mosaics occur when a chromosome is lost or gained during an aberrant cell division. Extra or missing chromosomes is usually lethal for the cell, but there are exceptions.
Conjoined twins are nearly always the same sex, but on rare occasions, one X chromosome is lost from one twin in an XY (male) embryo, giving one normal male twin and the other twin a female with Turner syndrome. People with Turner’s have only one X chromosome and no other sex chromosomes. The absence of a Y makes them female, but they lack ovaries and are thus sterile. Mosaic Down syndrome occurs in about 3% of Down syndrome cases. In mosaic Down’s, some cells are normal, and other cells have 3 copies of chromosome 21, the Down’s condition. Such a person’s appearance and mental condition are dependent on which cells are which. There is a case of a British admiral from the late 1700’s ( the height of the British navy—Horatio Hornblower days) whose portrait clearly showed he had Down syndrome, but who nevertheless was a brilliant admiral. (Unfortunately, I have been unable to track the details of this particular factoid down.) A related phenomenon: the human chimera. Starts out as fraternal twins, where the 2 embryos implant side by side in the uterus. This can result in the 2 embryos growing together, or one embryo incorporating the other within itself. Usually seen as a person with 2 different blood or tissue types, occasionally as a partially formed body within the person or disorganized hair, bone, teeth within the body. But could possibly result in different sex conjoined twins.
Interspecies Chimeras
• • • • • Human-mouse chimeras.
One method (not too controversial). Start with a mouse that has SCID: severe combined immuno-deficiency). This mouse has no functioning immune system and can’t detect or destroy invading organisms. Inject human lymph node cells, which develop into the immune system. The mouse develops an immune system consisting of human cells. This technique has been patented as the “scid-hu” mouse. It can be used to study the development of the immune system and to test drug toxicity in a system that is more similar to humans than the mouse immune system, but much less bound by ethical considerations than studies in humans.
More controversial: mix cells from human embryos and mouse embryos to form a chimeric embryo. Part of the debate on using human stem cells for research and medical therapy. Embryonic cells are much less restricted in what cell types they can develop into than adult cells. How does this creature develop? Mouse gestation time = 20 days vs. 9 months for human. Human sperm in a mouse? Etc. The “geep”, a goat-sheep chimera, was created by mixing embryonic cells of a goat and a sheep, then implanting the chimeric embryo into a surrogate mother. The resulting animals had patches of wool and goat fur, with various other intermediate structures.
Various other chimeras have been made by similar means: quail-chicken, for example.
Frankenstein • A man made from parts of others, re animated by an electric current.
• Why can’t we freely transplant body parts from one person to another?
Tissue Types
• Every cell has molecules on its surface that do a variety of jobs: attach to other cells, act as hormone receptors, transport materials in and out of the cell.
• Some of these proteins are involved in identifying the cell as a legitimate part of the body. These identification proteins are called “tissue type antigens” or histocompatibility antigens. They are the main cause for rejection of transplants.
Tissue Grafts
• Grafting within a person, or between genetically identical twins, is easy: all cells have the same cell surface proteins.
• Allografts: between different people, and xenografts: across species lines, don’t generally work because the cells have different surface proteins.
Histocompatibility Genes
• • • • Most of the cell surface proteins that cause differences between individuals are made by a set of genes called the “major histocompatiblity genes”, or MHC. There are hundreds of variants to these genes. Since we each have 2 copies of every gene, the number of unique combinations of these genes is very large, ensuring that most people have different tissue types. The person most likely to have the same tissue type as you is one of your siblings: a ¼ chance of having the same MHC genes as you do.
Other genes besides the MHC also control tissue type, making perfect matches between people very unlikely.
The Immune Response
• What happens when a tissue transplant occurs?
• The immune system has a group of cells called “killer T cells” that roam the body looking for foreign cells.
• Each killer T cell has a unique protein on its surface that will react with one specific matching protein. There are very many different types of T cell receptors, enough to detect almost any foreign body.
• Once a foreign object is recognized, the killer T cells either swallow it or bore holes in its membrane to kill it.
• Your own cells don’t get attacked because around the time of birth, all T cells that recognize anything in the body are killed: this is how “self” is distinguished from “non-self” • Autoimmune diseases start when T cells start recognizing some of your body cells as “non-self”. The T cells then kill your own body cells.
• Graft vs. host disease: when the T cells in the host’s body recognize the foreign graft and start to kill it.
Cyclosporin
• The first trick to successful grafts is to match tissue types as best as possible. This cuts down the number of T cell incompatibilites.
• The drug cyclosporin suppressed the immune response, making it possilbe for many transplants to occur • The bad side of cyclosporin: the body has a permanently weakened immune system.
Abominable Snowman
• • • • Human-like creature covered with fur who lives in remote parts of the world: the Himalayas in Asia, the US Pacific Northwest, the Ozark Mountains, various places in Canada, Iran, Africa, Australia.
“yeti” means “rock-living animal” in Tibetan. Westerners first spotted the yeti during mountain climbing expeditions in the 1920’s. The name “abominable snowman” is also a translation of a Tibetan term. One man even claimed to have been nursed back to health by a nine foot tall yeti. Photographs of 13 to 18 inch long footprints exist. Sir Edmund Hillary and Tenzing Norgay saw giant footprints during their ascent of Mt. Everest in 1953. In 1960, Hillary led a well-equipped, 11 month expedition to find the yeti. They never saw the animal, and the 3 skins they collected turned out to be from other animals. Hillary then decided that the yeti was mythical.
Bigfoot, or Sasquatch, has bee around since the late 1800’s. Numerous spottings and footprints, but no dead ones. Some movies have been made, but some are known fakes.
More Yeti
Bigfoot Story • In 1924 a Canadian lumberjack named Albert Ostman was prospecting near the coast of British Columbia when he was captured by a family of Bigfoots. The father and daughter guarded him while the mother and son prepared the meals. The family was vegetarian and ate roots, grass and spruce tips. After about a week Ostman was able to slip away. He didn't tell his story to anyone till 1957, fearing people would think he was insane. -
Neanderthals
• • • • • • In August 1856 workers in a limestone quarry in the Neander valley in Germany came across some bones that were undeniably human, but very odd looking, especially in the skull. Scientists held two differing views: they were either the bones of a modern human distorted by disease (a Cossack soldier fleeing Napolean’s army was a popular theory), or they were the bones of an human ancestor. Darwin’s
Origin of Species
was published in 1859, considerably adding to the controversy.
“Neanderthal” means “Neander Valley”. Often spelled without the h (Neandertal” to match the German pronunciation.
As time went on, more similar skeletons were found throughout Europe, and it became clear that the bones were quite ancient.
In 1864 Irish anatomist WIlliam King decided they represented a new species, christened “Homo neanderthalensis”. They were considered to be the ancestors of modern humans.
Neanderthal bones have been found across Europe and the Middle East, but not in Africa or eastern Asia. Neanderthals lived from approximately 200,000 years ago until about 30,000 years ago.
There are no human remains in the Americas older than about 30,000 years.
What did Neanderthals Look Like?
More Neanderthal Appearance
• • • Physical description: short, stocky, heavy build, large head, protruding brow ridges and a large nose. Their brain was as large or larger than ours. The oldest known was 40 years old when he died, and nearly all Neanderthal skeletons show signs of injury: healed bones.
Were they hairy like apes or smooth-skinned like us? When fist discovered, Neanderthals were thought to have been extremely primitive, closer to the apes than to us. We now know that there were many other human-like species that came between us and our common ancestor with the apes. In recent times Neanderthals have been thought to be very human-like in appearance and behavior. Certainly living in cold climates it seems likely that they wore clothing clothing exists.
—animal skins, probably, although no direct evidence for such A recent study of human lice bears on this subject. Head lice live in the hair, and they have been with us since long before we became human. Body lice, on the other hand, live in clothing. Body lice are a sub species of head lice. By examining the DNA of the 2 types, and comparing them to chimpanzee lice, it is clear that they diverged from each other fairly recently, about 70,000 years ago. This implies that early humans and Neanderthals may not have worn clothing. Neanderthals may have been hairy beasts after all. The evidence is pretty indirect and does rely on a number of assumptions.
Alternate Views
Neanderthal Behavior
• • • • Could they talk? It’s a little late for a conversation! An argument has been made that the structure of the base of the skull would not have allowed the larynx (voicebox) to produce the range of sounds that modern humans have. Another contribution to this controversy: in one skeleton, the hyoid bone in the throat (connects the tongue to the lower jaw) has been found. It is shaped like a modern human hyoid, and not like the hyoid bone in gorillas and chimps. Evidence for human-like behavior. Neanderthal bones are sometimes found in what look like funeral burials, arranged in a comfortable position. Some evidence that flowers were used to cover one of them. This evidence is controversial, however. In one case, Shanidar (named after the site), the person had had severe injuries, including destruction of an eye socket. These wounds were healed, and they were severe enough so that he wouldn’t have survived without assistance. A fragment of a flute has been found from Neanderthal times (50 000 years ago) It is bone, with holes spaced in a way that allows several modern style notes on it. They definitely made stone tools and used fire.
• • •
What happened to the Neanderthals?
About 35,000 years ago, modern humans came into their territory in western Europe. The modern humans are sometimes called “Cro-magnon”, based on the first archeological site they were found at. Although there is no obvious evidence of conflict, after several thousand years of co-existence, the Neanderthals apparently died out. Two competing theories. 1. The Neanderthals were the same species as modern humans, and the distinctive Neanderthal type disappeared by interbreeding. This implies that people of today carry Neanderthal genes. 2. Alternatively, the Neanderthals may have been an entirely different species, unable to produce fertile hybrids with modern humans. This implies that people today carry no Neanderthal genes.
Theories are tied up in a larger context. The older theory , called the “Multi-regional hypothesis”, says that all of the human-like creatures that lived in the past two million years or more (including Homo erectus, generally considered to be our ancestral species) are part of the same species, Homo sapiens, and that they evolved worldwide from the primitive forms into the forms we see today. The mechanism for the spread of new genes was a slow process of interbreeding between neighboring groups. This theory suggests that many of today’s populations have lived in the same area of the world for a very long time: the Chinese evolved in China, the Africans evolved in Africa, etc. The newer theory, called “Out of Africa” says that there have been many different species of human-like creatures, with Neanderthals just one of these species. Modern humans evolved in Africa about 100,000 years ago, then spread out from there. All other human species were eliminated.
• • • •
Evidence
The main evidence for the multiregional hypothesis comes from fossil bones. Anthropologists of this school claim to see the same regional differences in ancient bones as are present among the current inhabitants. Also, some skeletons are claimed to show intermediate characteristics between modern humans and Neanderthals. The out of Africa adherents say that bones are subject to deformation, and that the differences are too subtle to be real. I can’t judge these arguments.
The multi-regional hypothesis is currently losing ground due to DNA evidence. The DNA from 3 different Neanderthals has been examined, and the variant forms there are far outside the range of modern human DNA —at least twice as far from any modern human type as any two modern types are from each other. This implies that Neanderthals and modern humans last had a common ancestor 450,000 years ago, long before the encounters in western Europe.
Another aspect of DNA evidence is that modern human DNA is not very variable: there is more genetic variation among the chimpanzees in the Gombe Stream Reserve in Tanzania than there is among all human populations. This implies that somewhere around 100,000 years ago the human population went through a bottleneck —it was reduced to a very small number, from whom we are all descended. Most of the human DNA variation is found in Africa, and modern human remains have been found there of an appropriate age.
The DNA evidence mostly comes form the mitochondrial DNA, a small circle of DNA found outside the nucleus, in the mitochondria, the organelle that provides most of the energy to run the cell. This DNA is found in large amounts than nuclear DNA, and it is tougher —as a circle it has no free ends to attack. Mitochondrial DNA is inherited strictly through the mother, so it doesn’t give complete information about inheritence patterns in the species. For instance, if Neanderthal-human hybrids were only fertile with a modern mother and a Neanderthal father, we could have Neanderthal genes in us now, but not Neanderthal mitochondrial DNA. This type of situation; fertility in one direction but not the other —is very common in crosses between closely related species.
Human Evolution
Human Evolution
• At some point our lineage split with that of the Great Apes (gorilla, chimpanzee, bonobo, orangutuan). All creatures on the lineage after this spilt are called “hominids”. This split is thought to have occurred about 5.5 million years ago. After that time there have been a number of species of hominid, mostly living in Africa.
Hominid Evolution
• • • • The largest group of pre-human species was Australopithecus. Shortly after the ape/homnid split the species Autralopithecus afarensis lived. The best known example is the skeleton “Lucy”, which is almost complete. These creatures were 4 feet tall or less, but fully bipedal (walked on 2 legs all the time, unlike chimps and gorillas). They had large jaws and fairly small brains.
The hominid line split into 2 main branches after this time. One branch led to the modern humans, and the species on this line are in the genus Homo: Homo habilis, Homo erectus, Homo sapiens. The other branch contains several species that are called Paranthropus or continue to be called Australopithecus, or the “robust” Australopithicines. This branch developed very large jaws along with the sagital crest (on top of the skull) to support the jaw muscles. Big jaws, small brains ago.
—they seem to have been vegetarians. All species on this line died out more than 1 million years Our direct ancestral species was Homo erectus.
Homo erectus
• • • learned to create stone tools as long as 2 million years ago. Use of fire is more controversial. Some think fire use (if not the ability to make fire) came quite early, and that the gradual decrease in jaw size is a response to the use of fire to cook food. Others hold that fire use is a very late development, Homo sapiens only.
H. erectus did one other interesting thing: walked out of Africa and populated most of the Old World. This happened perhaps 1.8 million years ago. The “Out of Africa” theory really means Out of Africa Twice: once by Homo erectus, and them again by modern humans. The multiregionalists also believe that Homo erectus migrated out of Africa to the rest of the world (although they consider H. erectus to be primitive Homo sapiens and not a separate species). Could Homo erectus talk? The only real evidence against it is that the spinal column in the thorax in the best preserved skeleton is quite narrow. It has been argued that this implies an inability to control breathing well enough for speech.
Loch Ness Monster
• • • • • • Many large lakes seem to have resident sea monsters, and certainly the ocean is full of them. Lake Champlain in New York has “Champ”, and lakes Okanagan and Manitoba in Canada have Ogopogo and Manipogo.
The oldest story about he Loch Ness monster comes from 556 A.D., when St. Columba saved a swimmer from the monster by shouting at it.
Since roads first reached Loch Ness in 1937, Nessie has been spotted many times, and several pictures have been taken. The best picture has withstood a considerable amount of scientific analysis.
Unfortunately, this picture has been revealed to be a hoax, made of some plastic and a toy submarine. This hoax was created in response to yet another hoax. In 1939 the Daily Mail hired George Wetherall, a big game hunter, to find Nessie. He found some tracks and made plaster casts. When examined by a museum, the tracks proved to be those of a baby hippo, probably from someone’s umbrella stand. The Daily Mail was mad at Wetherall for having been hoaxed, and in revenge Wetherall came up with the plastic-enhanced toy submarine picture.
Loch Ness is large,deep, and full of peat —very hard to see into. Several expeditions have looked, but ambiguous photos have been the only results.
Realize that just 1 monster isn’t enough—you need a breeding population of them. No remains have ever been found.
Pleiosaurs
• The most popular candidate for Nessie and the other lake monsters is a dinosaur, the pleiosaur. Like all dinosaurs, pleiosaurs were reptiles, although the current belief is that they were warm blooded, like birds.
• Pleiosaurs had long legs, fat bodies, and flippers. They were carnivores. Like seals and whales, they evolved on the land, then took to the water later and had their limbs modified to flippers.
Extinction of the Dinosaurs
• • • • All dinosaurs are thought to have become extinct 65 million years ago, when a large object collided with the Earth. It left a crater in the Yucatan peninsula in Mexico, with an iridium-rich layer of ash and clay deposited over the entire world. The collision threw enough dust into the atmosphere to block sunlight for several years, leading to the collapse of food chains and the deaths of most large animals. Apparently no animal lager than about 50 pounds survived.
This theory was proposed by Berkeley physicist Luis Alvarez and his son Walter, in 1980, and it was once very controversial. Older theories had the dinosaurs dying of “genetic exhaustion” or climatic shift, or predation by mammals. The older theories were not very satisfying disappearance.
—lots of hand waving and no very clear explanation for the sudden The meteor theory has gained a lot by finding the iridium-rich clay layer everywhere on Earth that rocks of the proper age are exposed. Also, the Chixulub crater in Mexico is 100 miles in diameter and of the proper age. The idea that dust blocks photosynthesis comes from volcanic eruptions, such as Krakatoa in 1883 and Tambora in 1815. The latter caused “the year without a summer”, 1816, in New England —frosts as late as July, and the growing season cut in half. The global average temperature dropped by about 5 degrees Fahrenheit.