Keeping up with the Hominin

In less than a week, some of you will be shuffling back to school as Fall session begins. Every new semester, without a doubt, you'll be able to pick out the smart ass in the class. You know, the ones that sit in front of the class and always have their hands up when the professor asks a question (think Hermione Granger). But what if you are the smart ass? Have no fear, you're reading the right post.

"Hominin - the group consisting of modern humans, extinct human species and all our immediate ancestors (including members of the genera Homo, Australopithecus, Paranthropus and Ardipithecus)."

- Australian Museum.

A lot had happened this year with hominin research and some would redefine conventional understandings of this group. Below is a list of new studies that came out this year that I find quite interesting on hominin. Read up so you can show off in class with your knowledge of current hominin research. You know, just so you can make sure that your adjunct is really paying attention of what he/she is doing instead of begrudgingly teaching a class because he/she has to. Or maybe you have a geeky classmate you want to impress. Or if you're like me, you just wanna be the smartest in class because Asian Fail is not an option. So, enjoy ... and if they question you, tell them I said so.

Australopithecus africanus and Paranthropus robustus

• Male philopatry and female dispersal in both A. africanus and P. robustus. Is this a strategy to prevent inbreeding and mate choice by females? Ancient Hominid Males Stayed Home While Females Roamed, Study Finds

Paranthropus boisei

• Seems like we'll have to re-evaluate P. boisei's nickname, "Nutcracker Man". Recent study showed that P. boisei didn't eat nuts but instead used its big teeth to chew on grasses and sedges. No nuts for 'Nutcracker Man': Early human relative apparently chewed grass instead

From left to right: Comparison of upper jaw, P. boisei and H. sapiens. Photo from PhysOrg.

Homo erectus

• H. erectus were the first to controlled fire but it wasn't just used for warmth. New study shows that H. erectus were the first to cook their food (with fire) and process their food with tools. Homo Erectus Processed Food Like Humans, Harvard Scientists Say

• Stone artifacts, mostly flakes from stone tools, from the Dmanisi site in Georgia (the country, not the state) might suggests that H. erectus evolved outside of Africa. However, no conclusive evidence can be made due to the poor conditions of fossils found near these artifacts. Human ancestors in Eurasia earlier than thought

• H. erectus reached South Asia earlier than previously thought, between 1.5 to 1 million years ago according to Acheulean tools. Go east, ancient tool makers

• Findings from Solo River Terrace (SoRT) in Indonesia shows that H. erectus never coexisted with H. sapiens. Using three dating techniques: U-series, Electron Spin Resonance (ESR) and argon-argon, scientists found H. erectus went extinct between 143,000 to 550,000 years ago. H. sapiens are thought to reached Indonesia about 40,000 years ago. Human Ancestor Older Than Previously Thought; Finding Offers New Insights Into Evolution

An Acheulean hand ax found in India (South Asia) indicates that H. erectus moved to South Asia shortly after the invention of stone tools, around 1.6 million years ago. Photo from ScienceNews.

Homo neanderthalensis

• Neandertals probably died off because there were too many early humans to compete with. According to a statistical analysis, the Périgord region of southwestern France has the highest concentration of Neandertals and early humans. The ratio between Neandertal to early human was 1 to 10. There were just too many humans for Neanderthals to survive

• Mousterian culture might have lasted longer than previously thought and Neandertals might have spread as far as northern Russia in the mountains of Polar Urals, near the Arctic Circle. Last Neanderthals Near the Arctic Circle?

• Neandertals were predominantly right-handed, according to their teeth. Also, humans have been predominantly right-handed for at least 500,000 years. Neanderthal ancestors were mostly right-handed

Homo floresiensis (the Hobbits)

• The debate whether H. floresiensis is a separate species or just microcephalic H. sapiens continues on. New study shows that the measurement of the Hobbit skull is within the range of microcephalic H. sapiens. Taking the measure of a hobbit

From left to right: Homo floresiensis (LB1) and Homo sapiens.

Homo sapiens (early and modern humans)

• Early humans have been playing hanky panky with Neandertals and possibly the Denisovans. Proof? A toe bone and its DNA. Stone Age toe could redraw human family tree

• A particular segment of our X-chromosome were inherited from Neandertals. This supports the hypothesis that early humans interbred with Neandertal. However, only non-African humans have this segment. Confirmed: All non-African people are part Neanderthal

• Might not be a conscious decision, but apparently early humans that left Africa interbred with Neandertal to protect themselves against diseases. This is probably an unintended result more than an active thought process. First modern humans protected themselves against disease after leaving Africa by 'interbreeding with Neanderthals'

*Bouchra child, Homo sapiens*

• Dr. Harold Dribble and his team found the skull of "world's oldest human child" dated around 108,000 years old in Morocco and nicknamed it Bouchra. The boy died when he was 8 years old. This specimen has not been described in any scientific paper so watch out for it soon. World’s Oldest Child Found in Morocco

There are some Neandertal in us

Two papers published by Science on the May 7th 2010 issue posit that Neandertal genes exist in all of us (modern humans). The paper by Green et al. drafts the sequence of the Neandertal genome from three Neandertal individuals and compared them with the genomes of five modern humans, while the paper by Burbano et al. explains the method for sequencing target regions of Neandertal DNA.

John Hawks from John Hawks Weblog has a detailed write-up of these two papers. Check out his post, NEANDERTALS LIVE! Also check out Zacharoo's post from Lawn Chair Anthropology, Neandertal Nuclear Genome: Multiregional Evolution is the new Out of Africa.

The sequencing of the Neandertal genome brings back the age old question of human evolution: Multiregional or Out of Africa?

Link to papers:

• A Draft Sequence of the Neandertal Genome by Richard E. Green et al. (2010)
• Targeted Investigation of the Neandertal Genome by Array-Based Sequence Capture by Hernán A. Burbano et al. (2010)

Unearthed finger bone points to the possible discovery of an unknown hominin

DNA analysis from a finger bone unearthed from Denisova Cave, Siberia might lead to the discovery of an unknown hominin. Dubbed "X-Woman", information from her mitochondrial DNA suggests that she shared a last common ancestor with modern human and Neanderthals about one million years ago.

Since Neanderthals and modern humans split at about 500,000 year ago, it suggests that she did not originate from that divergent. Instead, she represents an unknown hominin lineage, presumably an unknown migration out of Africa. "X-Woman" is too young to be a descendant of Homo erectus (which migrated out of Africa to Asia about two million years ago) yet too old to be a descendant of Homo heidelbergensis.
 

"Whoever carried this mitochondrial genome out of Africa about a million years ago is some new creature that has not been on our radar screens so far," said co-author Professor Svante Paabo, also from the Max Planck Institute for Evolutionary Anthropology.

Read more about this discovery on BBC News, DNA identifies new ancient human.

Said article can be found on Nature, The complete mitochondrial DNA genome of an unknown hominin from southern Siberia (Krause et al., 2010). Unfortunately I do not have access to said journal so if you have a copy I'd appreciate it A LOT if you can send it to me. Thanks Mark, for the pdf.

*Edit* Here's a pdf from Nature, Fossil finger points to new human species.

Modern Humans Are Still Evolving But Will Modern Men Get Wimpier?

Two interesting articles that went into my inbox today: Modern man a wimp says anthropologist and Darwin Lives! Modern Humans Are Still Evolving.

A cover illustration from Australian anthropologist Peter McAllister's new book entitled "Manthropology" and sub-titled "The Science of the Inadequate Modern Male." Photo from REUTERS/Hachette Publishing/Handout.

Modern man a wimp says anthropologist  from Reuters, summarizes Peter McAllister's book Manthropology: The Science of the Inadequate Modern Male. Using various data from Neanderthals and ancient aboriginal populations, McAllister concludes that modern men are inferior than their predecessor in running, jumping, and even sheer brute. "Any Neanderthal woman could have beaten former bodybuilder and current California governor Arnold Schwarzenegger in an arm wrestle", McAllister said. John Hawks from John Hawks Weblog has a lot to say about this in his post Is modern man a "wimp"? I think Hawks is spot on with his post.

The Time article, Darwin Lives! Modern Humans Are Still Evolving, is about a study in a contemporary Massachusetts population led by Stephen Stearns and his team of scientists from Yale University. Using correlations between women's physical characteristics such as height, weight, blood pressure, and cholesterol levels with the numbers of offspring produced, they found that "stout, slightly plump, but not obese" women tend to have more offspring as oppose to women with very low body fat count, as well as women with lower blood pressure and lower cholesterol levels.

Stearns explains that women with very low body fat count, low blood pressure and low cholesterol levels do not ovulate. Ovulation is, of course, when the matured ovarian follicle ruptures and discharge an ovum (or the egg). While human females ovulate about once a month, female chickens ovulate once a day. Of course, we refer to chicken ovum as chicken eggs.

Stearns and his team thinks that the characteristics for producing maximum offspring (stout, slightly plump, higher blood pressure and cholesterol levels) were passed down from mothers to daughters. Separating social and cultural factors using statistical analysis, Stearns and his team were able to conclude that these characteristics were passed down genetically. "Variations in reproductive success still exist among humans, and therefore some traits related to fertility continue to be shaped by natural selection" Stearns says. So women who have more children are more likely to pass down these traits to their offspring.

It explains the notion that modern humans are still evolving because variation in reproductive success means that there are selective pressure that favor certain traits. Interesting to note that while fertility is being shaped by natural selection (as per Stearn and his team's study), artificial selection is also shaping the width of female pelvis and the average brain size of infants being born. Mothers with a narrow birth canal (smaller pelvis size) puts both her and her infant in jeopardy during childbirth. The infant will be stuck in the birth canal due to restricted space. An infant with a larger than average brain size will also get stuck in the birth canal. Both scenarios will likely kill the infant and mother. However the advent of Caesarean section negates the restriction of a narrow birth canal and allows infant with larger brain size to be born.

So, we can see that modern humans are evolving through variation in reproductive success, female pelvis size and average infant brain size is also evolving through artificial selection though it is too early to say which direction the selection is favoring.

Can I See Your Fingers Please?

That is what University of Liverpool's Emma Nelson probably would have said if she were to meet our hominan ancestors in person. Known to hold true in anthropoids (humans, apes and monkeys), the index (second digit) to ring (fourth digit) fingers ratio or 2D:4D is an indication of how much an individual were exposed to androgen (such as testosterone) in the womb. The more androgen you are exposed to, the longer the ring fingers are (and the shorter the index fingers are compared to the index fingers).

Photo of a human's left hand. From left to right: thumb, index, middle, ring and little finger. Photo modified from Wikipedia.

Nelson et al. believe that a high ratio (longer index finger, shorter ring finger) suggests monogamy (or pair-bonded) while a low ratio (shorter index finger, longer ring finger) suggests polygamy (or non pair-bonded). Simply put, individuals with high androgen level is likely to be non pair-bonded and the telltale sign is in the index and ring fingers. Also, some controversial studies had suggested that both men and women who receive high levels of androgen in the womb are more likely to be stronger, faster, and more sexually competitive.

Nelson and her researchers recently looked at the fossils of two Neandertals and one Australopithecus afarensis with complete index and ring fingers to determine their 2D:4D. They found that Neandertals had long ring fingers, suggesting that they were polygamous just like modern day primates that live in groups. A. afarensis on the other hand, had long index fingers. Nelson is puzzled by this discovery. "These were small creatures that probably lived in groups and were being eaten by predators. How do you keep from mating with different members of the group?", she said.

Indeed it does not make sense for A. afarensis to be monogamous if they live in groups. Notice that Nelson et al. only used one A. afarensis fossil to get the 2D:4D. Perhaps it is not their fault that only one A. afarensis specimen had complete index and ring fingers but such are the dilemma of using fossil specimens to generalize a whole species.The result might just be a statistical outlier. However, I can't speculate the result or the implications but anyone that are familiar with statistical data knows that a small sample size leads to a higher sampling error. Also what would a 2D:4D = 1 (same index and ring finger length) be?

Interesting enough, John Hawks at John Hawk's Weblog mentioned the correlation of 2D:4D with male homosexuality (Robinson and Manning, 2000). I would know about this. In fact, my 2D:4D is indeed low.  Robinson and Manning predicted right! Maybe ...

I do find both Nelson et al. and Robinson and Manning (2000) research interesting but I would like to stress that the results are mere predictors and correlations. Take it with a grain of salt. Don't go measuring 2D:4D of your future spouse, boyfriend or girlfriend and accuse them of not being monogamous or a homosexual.

Emma Nelson and her team presented their research at this year's Society for Vertebrate Paleontology meeting held in Bristol, United Kingdom. Read more about Emma Nelson's research.

References:

Reilly M. 2009. Human Ancestors Conflicted on Monogamy. Discovery News. Retrieved September 25, 2009, from http://dsc.discovery.com/news/2009/09/24/human-monogamy.html

Robinson SJ. Manning JT. 2000. The ratio of 2nd to 4th digit length and male homosexuality. Evolution and Human Behavior 21(5): 333-345. [doi:10.1016/S1090-5138(00)00052-0]

Homo floresiensis Walked Out of Africa

Skull of LB1 (Homo floresiensis, or the hobbit). Photo from Science Museum

New analysis by a team led by Australian National University doctoral student Debbie Argue showed that Homo floresiensis, nicknamed hobbits, were early hominin and walked out of Africa to Flores. Their findings supports the argument that Homo floresiensis had a unique wrist anatomy that originated from a lineage that lived long before the common ancestor of Homo sapiens and Neanderthals.

With Mike Moorwood from University of Wollongong and Thomas Sutikna from Indonesian Center for Archaeology, Debbie Argue compared 60 skulls and skeletal features from two individual hobbits to those of hominins, chimpanzees and gorillas using cladistic analysis. The result shows that Homo floresiensis "probably took one of two evolutionary paths from Africa to Flores. One began 1.66 million years ago, the other 1.9 million years ago".

Read more here: Hobbits Walked Out of Africa

The Face Of The First European

The face of the first European, reconstructed by forensic artist Richard Neave. Photo from Telegraph.

Using the incomplete skull and jaw bone in a cave in the southwest of the Carpathian Mountains in Romania, scientists had revealed for the first time the face of the first European.

Scientists doesn't know if this modern human is a male or a female but using radiocarbon analysis they found that this individual lived around 34,000 to 36,000 years ago. Around this time, Europe is home to both Neanderthals and modern humans. Modern humans first arrive to Europe from Africa.

The skull of this individual is human-like, though there are also some archaic traits such as large molars. Some scientists speculated that this skull belongs to a Neanderthal and modern human hybrid though it was disproved by many experts.

Richard Neave, a forensic artist used clay to reconstruct this individual for a BBC program about the origins of the human race and evolution.

Study Confirms 3 Distinct Sub-Groups Of Neanderthals

Research by Fabre et al. (2009) in Genetic Evidence of Geographical Groups among Neanderthals using models from genetics, demography and paleoanthropology confirms that there are 3 distinct sub-groups of Neanderthals; ones in Western Europe, Southern Europe and Western Asia. The size of the three populations was not constant, possibly indicating migration between populations.

Read the press release and article from PLoS ONE: Genetic Evidence of Geographical Groups among Neanderthals

Were Neanderthals Cannibals?

Were Neanderthals Cannibals? Archaeological evidence from Krapina, Croatia shows that Neanderthal fossils exhibited signs of cannibalism, including cut marks. Did Neanderthals eat each other? Exploited a new "food" source when times were harsh? Not so fast, said paleoanthropologist and archaeologist Jörg Orschiedt from the University of Hamburg in Germany. He said that cut marks in the Krapina sample were randomly distributed and were not necessarily in locations where defleshing generally occurs, which is where the muscles attach themselves to the bones. Orschiedt thinks that the cut marks come from researchers that were measuring these bones with sharp measuring tools.

Read the rest of the article from Scientific American.