This picture, known as the "march of progress," is an example of a common evolutionary misconception. It gives the impression that humans evolved from apes, when in truth humans are more like distant cousins of apes because we share a common ancestor. We did not come from apes directly.
Here's an interesting article
that lists 5 traits that the author thinks humans will possess in the future. Although this article is a fun read, many of the points are debatable. For example, the author thinks that humans will be more resistant to heart disease
in the future because they are currently leading causes of death. But is susceptibility to heart disease and diabetes really being selected against if these diseases usually manifest after reproduction?
Here's a great interactive documentary
that tells the story of human origin.
describes how the finding of a rare complete skull of a human ancestor has caused scientists to identify a different, controversial evolution story in the genus homo. Here is a link to a great book
about our ancestral relationship with chimps and bonobos that describes many of the similarities we share as species.
If you want to know a little more history about evolution here is a website
that goes over it in detail. It also discusses why people have an issue with evolution and their beliefs against it. It also discusses Darwin's journey and significant figures in his voyage. I found it very interesting because it showed me insights why people disagree with evolution.
Something interesting to note, as there is evidence that there were at one point in history many different hominoid species present on earth at the same time, as recently as was noted in lecture up to 250 years ago. The reason for Homo sapiens continued existence while others were eventually became extinct is a mystery. But brain size could have been a key evolutionary and adaptory selection that proceeded to be favorable for our species.
Hominids - members of the clade containing humans (Homo), chimpanzees and bonobos (Pan), gorillas (Gorilla), and orangutans (Pongo) aka Great Apes
Neanderthals (Homo sapiens neanderthalensis)
So similar, yet so different...
Here's a documentary on the rise of our own human species and the extinction of neanderthals.
Interesting article here:
- Neanderthals are our closest extinct human relative.
- They existed around 600,000 to 350,000 years ago in parts of Europe.
- Defining features: large middle part of face, angled cheek bones, big nose, smaller and more angular forehead, shorter and stockier body
Here's an article from the NY Times explaining how paleoanthropologists have used fossil and genetic data to identify a previously unknown species of humans, a cousin to the Neanderthals
, that may have existed 25,000 years ago, living alongside Homo Sapiens and possibly mating with them.
This article about the interbreeding of hominins
suggests that humans evolved from many different human species. In Europeans and Asians, they found that 2.5 of living human European and Asian DNA came from neanderthals, but this DNA was not present in Africans. In populations of the Australian Aborigines, the Philippines, New Guinea, and an island called Bougainville, remains of the genome of another hominin called Denisovans were found. These hominins were distantly related to Neanderthals. Also, in Africans, they found 2 percent of their genome to seem out of place, possibly giving evidence to another hominin that may have interbred with others. All this data gives evidence that humans evolved from the interbreeding of hominins.
comparing neanderthal mitochondrial DNA, and modern day human mtDNA. It shows evidence supporting the idea that neanderthals did not contribute substantially to the modern human genome
. However, Neanderthal alleles are still present in the human genome today due to hybridization.
Here's a good article
on how human hands evolved before walking did. Namely, our senses the way they are now came into being before our ability to walk did.
Here's an article
on how recent fossil evidence may suggest a simpler evolutionary history for the genus Homo.
Evidence of Neandertal and Homo sapiens Interbreeding
Interesting new article about fossils thought to come from this cross can be found here.
Videos and links:
Here is a link to a great video that outlines facts about human evolution.
Here is an awesome documentary on the orgins of homo sapiens, and the science behind their evolution, biology, and ancestory
- This is an interesting look into the history of studying the evolution of altruism in humans
- William Hamilton's theory in 1964: Genes for altruism could evolve if the benefit of an action exceeded the cost to the individual once relatedness was accounted for: inclusive fitness theory
Our ability to sequence the human genome at incredible speeds is rapidly modifying our conceptualization of human evolutionary history. Watch Dr. Resnick
give a talk about the "genomic revolution."
The ability to sequence the human genome has made incredible leaps and bounds since it was first sequenced in The Human Genome Project (completed 2003). The HGP originally cost $2.7 billion, and now you can have your own personal genome sequenced for only $99 by 23 and Me
Y Chromosome Uncovers New Clues About Human Ancestry
- DNA and fossil evidence both show that humans and chimpanzees shared a common ancestor 7-10 million years ago. (new scientist)
The full article from Science Daily can be found here
- Humans originated from a few common ancestors that migrated all over the Earth, creating a large diversity in the population that we see today.
- Past studies have utilized DNA from mitochondria to map the evolutionary branching of females.
- The analysis shows that the females' most recent common ancestor lived between 99,000 and 148,000 years ago.
- Scientists have developed a new technique to compare the DNA sequence of Y chromosomes in males across many different populations.
- The analysis shows that the males' most recent common ancestor lived between 120,000 and 156,000 years ago.
- The agreement between the two findings makes the individual and collective results that much more significant.
Recently, scientists have discovered
a much more ancient root to the Y tree dating to before the first anatomically modern human fossils. This suggests a more complex process underlying the origin of Y chromosome diversity, as well as the need to be cautious of the stochastic nature of the genealogical process when inferring data from a single locus.
The Out of Africa Theory
This is generally the most widely accepted theory for describing the migration of Homo sapiens out of affrica and into othe parts of the globe. Many studies, fossil discoveries, and genetic analysis continues to back up this theory.
Scientist and fossil evidence suggest that the first Homo sapien
developed and evolved to anatomically modern humans on the African continent. Fossil evidence suggests this occurred between 200,000 and 150,000 years ago. It is also proposed that the first migrations out of Africa began sometime between 125,000 and 60,000 years ago.
"Getting here from there"
This is an article about how certain genes have passed from different generations of humans in the Americas via the Bering Strait. Great tree of the genes with their holders is present in the article.
Evolution of the Immune system
Part of the human immune system, the adaptive immune system, is thought to have evolved because of the presence of parasitic worms. Helminth worms evolved and began infecting many different human organs around the same time that the adaptive function of our immune system became common. More information can be found here.
Evolution of the Innate Immune System
Read this article (pdf) for an analysis of the molecular mechanisms of the innate immune system in humans and a demonstration of the highly conserved nature of this system in both vertebrates and invertebrates.
Phenylketonuria - a pleiotropic disease
- Pleiotropy - one gene influences multiple, seemingly unrelated phenotypic traits
- Example of this is PKU (phenylketonuria) - this disease causes intellectual disabilities and reduced hair/skin pigmentation
- Caused by mutations in single gene that codes for enzyme which converts phenylalanine (F) to tyrosine (Y). Conversion under PKU is either dramatically reduced or lost entirely. This unconverted aa can rise to toxic levels in the bloodstream and affect brain and nervous system function
- Mutated gene ➞ insufficient enzyme conversion ➞ affect on phenotypic traits ➞ pleiotropy!
Evolution of Tools
Oldowan tools - earliest stone tool industry, aka "pebble tools" include choppers, scrapers, and pounders
Evolution of Furlessness
Some researchers theorize that hairlessness evolved in response to humans' long-distance travel behavior. Hairlessness may have been adaptive in humans' travel across the heat of the African savannah.
Other theories include the idea that humans went through a semi-aquatic phase or that hairlessness evolved as an adaptation for persistence hunting - long-distance tracking and chasing of an animal until it collapses of exhaustion.
Evolution of Sleep
There are many theories as to why humans need sleep. One of the most common theories is that we sleep to solidify memories. There have been many studies done proving a correlation between lack of sleep and memory loss. Other theories pose the idea that we sleep not only to solidify memories, but also to prune them. While we seep, we 'prune' certain synapses. Some scientists hypothesize that this is what causes us to dream.
Another theory as to why we sleep is that it helps us fight infections. There have been many studies done in animals that show that the number of white blood cells in an animal increases as the amount of sleep an animal gets increases, as well as the fact that the number of pathogens a species contracts decreases as the amount of sleep increases.
Boston University conducted a Phylogeny of Sleep project to comprise a database of sleep quotas of mammals.
The Evolution of Aging
Some experts theorize that aging and an upper age limit may be selected for in a population, because it may be detrimental to a population for older organisms to continue to live when they consume more resources than they contribute.
- Aging (senescence) is "an inevitable progressive deterioration of physiological function with increasing age."
- Aging is often characterized by an age-dependent increase in mortality and decline of fecundity (Rose 1991, Bronikowksi & Flatt 2010)
- This poses an evolutionary paradox: Natural Selection designs organisms for optimal survival and reproductive success (Darwinian fitness), so why does evolution not prevent aging in the first place?
- A possible explanation is that aging is controlled by telomeres, and that telomeres that are too long cause genetic problems. More information about telomeres and aging can be found here.
- The force of selection declines with age.
- The parsimonious approach for explaining the existence of aging relates to individual fitness and selection instead of an entire group
- Aging itself is related to the existence and length of telomeres, which are the segments at the end of each chromosome arm consisting of a series of repeated DNA sequences that regulate chromosomal replication at each cell division. Some of the telomere is lost each time a cell divides, and when the telomere is exhausted the cell dies (definition from NIH)--Stress has been shown to increase speed of telomere degradation (source: Escape Fire, The Fight to Save American Healthcare).
- This article discusses how free radicals damage cells and cause aging.
Evolution of Language
- The above article suggests that language is unique to humans because humans have a set of particular psychological mechanisms.
- Further reading is provided at the end of the article.
The article above is an explanation of more information regarding the evolution of language.
The theory follows the fact that although there are a lot of possibilities for language, they all base from the same cognitive approach. For example the article states that of "6 possible combinations of subject, verb and object there are only 2 that are found in more than 90% of all languages."
discusses the origins of human speech and when exactly human speech evolved.
discusses the evolution of human speech and claims that language originated in central or southern Africa, and most modern languages have a common root.
The Evolution of Blood Types
The Various blood types, A,B,O, are not only found in humans, but also in chimps, gibbons, and other primates. In order to explain this, a study was done
that found that A and B blood types had been around for at least 20 million years, which was well begore the chimp-human split.
The Evolution of Kissing
Ever wonder why humans kiss to show affection? Truth is, many animals from squirrels to elephants engage in some sort of behavior that could be equated to this seemingly unique human action. Kissing is thought to be a purely social and sexual activity, but it could have implications ranging from the compatibility of mating to showing that we are altruistic. To learn more read this article on the evolution of kissing
- chimpanzees have actually been shown to kiss after fights in a display of reconciliation
- one theory of the emergence of kissing revolves around the practice of passing pre-chewed food from the mouth of one animal to another, usually a baby
Here is another article with more information about the evolution of kissing.
Major Histocompatibility Complex and Sexual Selection
The Major Histocompatibility Complex (MHC) is an antigen that exists on the cell surface, and is related to the immune system. It is believed that chemosensation of this complex in humans is used in mate selection, as it allows for an individual to determine the innate resistances that the potential mate has. Logically, it would follow that an individual would seek someone with a varied innate immune system to raise the chances that their offspring will have resistance to a wider variety of diseases, making them more fit. The MHC experiments also indicate that organisms tend to seek diversity in mates. The MHC is something that can be innately sensed something like a pheromone, and the MHC genes have significant diversity among humans. Seeking diversity in a mate helps increase genetic variation in offspring.
Here are a few wikipedia articles to begin reading about the MHC and sexual selection:http://en.wikipedia.org/wiki/Major_Histocompatibility_Complex_and_Sexual_Selectionhttp://en.wikipedia.org/wiki/Interpersonal_compatibility
Assisted Reproduction Technology in Humans
Assisted reproductive technology (ART) are methods used to achieve pregnancy by artificial or partially artificial means. It is reproductive technology used primarily for infertility treatments, and is also known as fertility treatment.How does assisted reproduction technology such as in vitro fertilization affect human evolution?
- Scientists have discovered a way to turn skin cells into eggs and sperm in mice.
- They do this by forcing skin cells into induced pluripotent stem cells.
- They implanted these cells into infertile mice and one in four amazingly became fertile!
- There are still issues with the science. The naturally occurring PCG run a high risk for genetic diseases.
- This science could lead to solutions for infertile individuals in our own species! This could cause infertile individuals to have the capability of passing down their genes, which would make them more evolutionarily fit!
The Future of Human Evolution
Here is a link to an NPR program concerning human evolution and how it may proceed in the future
Cooking and its Role in Evolution
Some scientists hypothesize that the fact that early humans cooked their food allowed them to evolve into the complex beings they are today. If we had continued to be herbivores, we would have spent many hours each day simply acquiring and chewing our food. Cooking our food allowed us to eat and digest our food much quicker, which gave us more energy and the ability to develop and feed our brains, which allowed them to grow to a tremendous size. The full article can be found here
Humans: omnivores or herbivores?
There are always evolutionary advantages to being able to consume more varied sources of food. Humans and primates are relatively unique in their ability to thrive without the exclusive consumption of meat and remain omnivores. Omnivores are slower to diversify than herbivores and evolve, which is a tradeoff for their ability to draw nutrients from various sources. Humans have the typical GI flora for omnivores, however their anatomy is similar to herbivores in many ways. Most herbivores and humans both have long colons, moderate urine concentration, stomach acidity of pH 4-5 and blunted flat teeth. The addition of consumption of meat to the human diet allowed them to begin weening children off of breastfeeding sooner and allowed for development of the brain through the cooking of food, specifically meat.
This article discusses the issue further.
It is thought that that ability to digest meat protein among vegetables led to the development of humans large brain capacity.
Humans developed lactose tolerance into adulthood around 8,000 years ago. It is thought that the ability to break down lactose must have been beneficial for survival for the gene to continue into further generations. Aside from the nutritional benefits of drinking milk when food sources are scant, it is thought that being able to digest lactose would be beneficial because it provided an alternative source of liquid. Water was often contaminated, and the ability to drink milk would confer a survival advantage to those who lived in areas with less than clean water. These people who did not have clean water needed to have the cattle, and thus access to milk, to develop the tolerance. This article expounds upon this idea more.
Here is an article that thoroughly explains lactose intolerance.
An Evolving Population
- The following TED talk discusses the evolution of humans from beginning to end.
- Addresses the ever evolving human population and poses a question: Will Our Kids be a Different Species?
- Catch Juan Enriquez's TED Talk here!
Human Evolution Over?
When considering human evolution, we look back on the thousands of years it took natural selection to produce the modern-day man. But is the human species still changing or evolving?
This article from a UK newspaper talks about how Sir David Attenborough, a British natural history filmmaker, believes that human beings have reached the end of the road for evolution. He supports his claim by giving the example of babies surviving who normally in the past would have died within hours of being born due to technological advances, and thus stopping the forces of Natural Selection. However, geneticist Dr. Rutherford rebuts by saying that we cannot say this due to our long time span. He states many reasons for why Attenborough is not correct, and says that only thousands of years later can we truly try to answer the question: are humans still evolving?
Professor at the University College in London is in agreement with Sir David Attenborough that human evolution has in fact reached an end, due to increasing lack of genetic diversity. Here is an excerpt from his discussion on the topic.
An article from US News and World Report in 2008 ( http://www.usnews.com/science/articles/2008/07/24/where-is-human-evolution-heading) argues that human is not over and references many of the thing we discuss in class, from full gene sequencing of new mutations to examples of farming and developing lactose tolerance. After all, evolution doesn't always happen overnight, and in many cases, may need to be looked at in retrospect. A clue to how humans may be evolving is that some people no longer have wisdom teeth like our ancestors did. One resource claims that 35% of the human population is born without wisdom teeth. Perhaps in the future, the wisdom-teeth-less trait will go to fixation.
Henry Harpending, a professor of anthropology at the University of Utah, claims that humans are not only evolving, but they are evolving faster than ever before. "Human races are evolving away from each other ... Genes are evolving fast in Europe, Asia and Africa, but almost all of these are unique to their continent of origin. We are getting less alike, not merging into a single, mixed humanity." He claims that this phenomena was caused by humans diverging from Africa, "and there has not been much flow of genes between the regions since then".
This article states that humans are still evolving due to Natural Selection as a result of variations in women's fertility.
New Info About Human Evolution From New Found Skulls
- This article talks about 5 skulls that were recently found.
- These are the oldest skulls from Homo Erectus found to date outside of Africa.
- Read about it here and see what the implications of this discovery are regarding human evolution. Here is another article that further validates this discovery and discusses the controversy behind rewriting human evolutionary history.
- A separate article, found here, suggest that snakes helped to shape the primate brain!
Evolution of Human Running
- This article expands on what we talked about in lecture about the evolution and history of running.
- It explores the anatomy and features of humans that are specific for running, not walking in humans, and the role that running served in our ancestors.
- Here's an article that is an example of persistent hunting. Unlike the video we saw in class, the hunters were successfully able to hunt down a cheetah.
- Here's an article that contradicts what we learned in class. The author doesn't believe in the theory that humans evolved to be long distance runners because of persistence hunting.
Here is a picture that shows the similarities between human and ape feet. These structural differences are major contributors to our ability to run:
Human evolution is the evolutionary process that began with the last universal common ancestor and is currently at modern humans (Homo sapien). It is likely that the common ancestor of humans and chimpanzees diverged 7.2 million years ago (Wilkinson 2011). This disproves the idea that humans are merely the more evolved form of primates. *Humans did NOT evolve FROM monkeys, Humans and Chimpanzees share a common ancestor!* It is important to understand that, though we are unique, we are not any more complex than any other species. We are extremely well adapted to environment, which makes us strive and progress, but there are plenty of other species that could be considered "complex" because they are equally adapted to their environment.
- loss of muscle structure in the hands
- this allows better mobility in the hands so that one can create tools for hunting however, the ability to be good at climbing trees declines
- legs underneath
- more efficient for walking, which had additional structural changes to the posture and gait of humans, forcing a straighter back than a hunched one for efficiency.
- Hands became smaller
- allowed for building or crafting of more specialized tools
- Increased brain to body size ratio
- allowed for higher cognitive ability → art, emotions etc.
- Here is an article on the evolution of the human mind.
Development of Bipedalism
The bipedalism foot is an adaptation seen in hominins that is not seen in our most recent common ancestor (who's feet resemble hands). Ardipithecus, found 4.2 mya, is the oldest fossil showing suited for bipedalism. Bipedalism is accompanied by many other adaptations as humans evolved the ability to walk upright.
- Plantar arch develops
- Pelvis narrows
- Achilles tendon lengthens
- Legs grow longer
- Non-opposable big toe (hallux)
- Article about how new robotic artificial limbs are able to mimic human legs. Since we talked about how important the development of walking was to humans in class, I thought the fact new advances in technology could mimic the natural walking pattern of humans was interesting.
- Bipedalism was a key aspect in human evolution in terms of nutrient availability, hunting, and brain size/body ratio development.
Evidence from Fossil Record
Evidence from Molecular Genetics
Evolution in Mountain Populations of Humans
One of the best examples of human evolution that is very observable is the difference between humans living in high altitudes and low altitudes. There are many difficulties associated with living at high altitudes since there is less oxygen, but there are many populations of humans that have lived there for many years. There are many biological adaptations in high altitude populations. For example, Andes populations can dissolve more oxygen in their blood, while Tibetans have broader blood vessels. Doctor Rasmus Nielsen published multiple studies on the genomes of highland populations. In his studies, he found that they had gene variants that were not common in surrounding low altitude populations, such as the EPAS1 gene variant found in Tibetans that affects levels of hemoglobin in blood. In a highland population in Ethiopia, he did not find that EPAS1 gene had evolved like it did in Tibetans. Instead, he found that the BHLHE41 gene had gone through selection. These two different genes were selected to help the populations survive to the same environment.
This is a really cool article on how the Sherpa People's genome may have changed because of their environment living high up in the mountains.
Different Theories Used to Analyze Human Evolution
- Recent African Origin (RAO) hypothesis: humans evolved in a certain area in Africa, and then spread out to other areas of the world. Evolution of humans is younger in this hypothesis. This hypothesis seems to be more accepted.
- Multiregional evolution hypothesis: humans experienced evolution from various groups of Homo erectus in different locations. Evolution of humans is much older in this hypothesis.
- Read more about these hypotheses here
Human Evolution in Space
What effects might living in space have on the human species? Differences in gravity, air content, and radiation levels may all have a huge impact on human populations in space.
This article goes into detail of four predictions of future human evolution. The article also includes theories on whether or not humans will evolve into life in space. Article found here.
This article about the fear of snakes says that this fear evolved in our ancestors a long time ago. Various monkeys that have never seen snakes in their life still showed strong responses to pictures of snakes, showing that a common ancestor of ours. Dr. Lynne A. Isbell along with other neuroscientists pinpointed a cluster of neurons in primate pulvinars. They found out that this region evolved for recognizing snakes. The article also states that many traits that make primates unique evolved as defenses against snakes.
Human Evolution Proof
Since we had a test question
over the proof of whether or not Homo sapiens
came out of Africa or evolved from the various other species of Homo that have been found around the world, I found this article that has bullet pointed the specific
arguments of each argument.