Sunday, 29 December 2013

[RwandaLibre] What We Learned About Human Origins in 2013


What We Learned About Human Origins in 2013 - 4 hrs ago

The existence of a mysterious ancient human lineage and the
possibility that the earliest humans were actually all one species
were among the human-evolution-related discoveries of 2013. Other
breakthroughs include the sequencing of the oldest human DNA yet.

Here's a look at what scientists learned about humanity and human
origins this year:

Mystery lineage

Recent analyses of fossil DNA have revealed that modern humans
occasionally had sex and produced offspring not only with Neanderthals
but also with Denisovans, a relatively newfound lineage whosegenetic
signatureapparently extended from Siberia to the Pacific islands of

This year, hints began emerging that another mystery human lineage was
part of this genetic mix as well. Now, the first high-quality genome
sequence from a Neanderthal has confirmed those suspicions.

These findings come from Denisova Cave in southern Siberia, where the
first evidence of Denisovans was discovered in 2008. To learn more
about the Denisovans, scientists examined DNA from a toe bone
unearthed there in 2010.

The researchers found that the fossil belonged to a Neanderthal woman.
Her DNA helped refine the human family tree, as it revealed that about
1.5 to 2.1 percent of the DNA of modern people outside Africa is
Neanderthal in origin, whereas about 0.2 percent of DNA of mainland
Asians and Native Americans is Denisovan in origin. [Top 10 Mysteries
of the First Humans]

The scientists also discovered that the Denisovans interbred with an
unknown human lineage, getting as much as 2.7 to 5.8 percent of their
genomes from it. This newfound relative apparently split from the
ancestors of all modern humans, Neanderthals and Denisovans between 4
million and 900,000 years ago, before these latter groups started
diverging from each other. It's possible that this mysterious lineage
could even be Homo erectus, the earliest known undisputed predecessor
of modern humans. However, there are no signs that this unknown group
interbred with modern humans or Neanderthals.

Genetic analysis also revealed that the parents of this Neanderthal
woman were closely related — possibly half-siblings, or another close
relative. (Inbreeding may have been common among early humans — it
remains uncertain as to whether it was some kind of cultural practice
or whether it was unavoidable due to small community populations at
the time.)

Were earliest humans all one species?

Modern humans, Homo sapiens, are the only living member of the human
lineage, Homo, which is thought to have arisen in Africa about 2
million years ago at the beginning of the Ice Age. Many now-extinct
human species were thought to once roam the planet, such as Homo
habilis, which is suspected to be among the first stone-tool makers;
the relatively larger-brained Homo rudolfensis; the relatively slender
Homo ergaster; and Homo erectus, the first to regularly keep the tools
it made.

The level of variation seen in Homo fossils is typically used to
define separate species. However, analysis of 1.8-million-year-old
skulls excavated from the Republic of Georgia revealed the level of
variation seen among those skulls was about the same as that seen
among ancient African Homo fossils. As such, researchers suggest the
earliest Homo fossils may not be multiple human species, but rather
variants of a single lineage that emerged from Africa. In other words,
instead of Africa once being home to multiple human species such as
Homo erectus, Homo habilis, Homo ergaster and Homo rudolfensis, all of
these specimens may actually simply be Homo erectus.

Oldest human DNA

The testing of the oldest known human DNA added more evidence that
human evolution was complex.

The genetic material, some 400,000 years old, came from a human
thighbone unearthed in the Sima de los Huesos, or "Pit of Bones," an
underground cave in northern Spain. Until now, the previous oldest
known human DNA had come from a 100,000-year-old Neanderthal from a
Belgian cave.

The fossils unearthed at the site resembled those of Neanderthals, so
researchers expected the ancient DNA they analyzed to be Neanderthal
as well. Surprisingly, the DNA revealed that this fossil's closest
known relatives were not Neanderthals but Denisovans. This finding is
strange, scientists said, because studies to date currently suggest
the Denisovans lived in eastern Asia, not in western Europe, where
this fossil was uncovered. One possible explanation is that a
currently unknown human lineage brought Denisovan-like DNA into the
Pit of Bones region, and possibly also to the Denisovans in Asia.

Evolution of tool use

The capability to make and use complex tools is a critical trait
distinguishing modern humans from all other species alive today. Now,
scientists have found an ancient hand-bone fossil that reveals that
the modern human ability to make and use complex tools may have
originated far earlier than previously thought.

A key anatomical feature of the modern human hand is the third
metacarpal, a bone in the palm that connects the middle finger to the
wrist. A little projection of bone known as a styloid process in this
bone helps the thumb and fingers apply greater amounts of pressure to
the wrist and palm. Researchers had thought the styloid process was a
relatively recent feature, perhaps evolving close to the origin of
modern humans. However, scientists have discovered a
1.4-million-year-old fossil that possesses this vital anatomical
feature, meaning it existed more than 500,000 years earlier than it
was previously known to have existed and was perhaps fundamental to
the evolution of the whole genus Homo, not just modern humans.

This hand bone may not be the only key trait for tool use that evolved
near the origin of the human lineage. Humans are the only species that
can throw with great speed and precision, and scientists found this
ability first evolved nearly 2 million years ago with anatomical
changes to the shoulder, arm and torso. This advance likely boosted
the hunting prowess of now-extinct human ancestors, helping them
effectively and safely kill big game.

Neanderthal discoveries

In 2013, researchers also made important discoveries about
Neanderthals, modern humans' closest extinct relatives. For instance,
analysis of a Neanderthal tomb in France suggests that, like modern
humans, Neanderthals may have intentionally buried their dead. The new
findings are further evidence that Neanderthals might have possessed
complex forms of thought, enough for special treatment of the dead.

In addition, a cache of Neanderthal fossils discovered in a cave in
Greece suggests the area may have been a key crossroad for ancient
humans. The age of these fossils suggests Neanderthals and other
humans may have had the opportunity to cross paths there, and even
interact, the researchers added.

Follow us @livescience, Facebook & Google+. Original article on LiveScience.
Denisovan Gallery: Tracing the Genetics of Human Ancestors Top 10
Things that Make Humans Special Top 10 Missing Links Copyright 2013
LiveScience, a TechMediaNetwork company. All rights reserved. This
material may not be published, broadcast, rewritten or redistributed.


So let me get this right. #$%$ Sapiens sapiens evolved in Africa and
some of which left Africa about 100,000 years ago. Whilst in an area
between the Persian Gulf, Anatolia and the Caucasus they interbred to
a small degree with Neanderthals and even less with Denisovans and
another group of #$%$ of which we only have evidence of their DNA at
the same time #$%$ sapiens, sapiens was moving along the coast towards
India. At a later date this admixture moved east both below and above
the Himalayas and a small number moved west of which we have no
descendants today.

Richard, 2 hrs ago

"Modern humans, #$%$ sapiens, are the only living member of the human
lineage, #$%$, which is thought to have arisen in Africa about 2
million years ago at the beginning of the Ice Age." lol oh becareful
yahoo, wouldnt want to shake up the fan club of the abrahamic myth
with facts. You see, they posit that dinosaurs were created by a super
genie sky daddy 6,000 years ago, and they died 5,000 years ago...yes
yes i know we have all of those fossils showing they died millions of
years ago, but there you go again waving facts in the face of

GoodWithoutgod, 2 hrs ago

Evidence of common descent of living things has been discovered by
scientists working in a variety of fields over many years. This
evidence has demonstrated and verified the occurrence of evolution and
provided a wealth of information on the natural processes by which the
variety and diversity of life on Earth developed. This evidence
supports the modern evolutionary synthesis, the current scientific
theory that explains how and why life changes over time. Evolutionary
biologists document evidence of common descent: making testable
predictions, testing hypotheses, and developing theories that
illustrate and describe its causes. Comparison of the DNA genetic
sequences of organisms has revealed that organisms that are
phylogenetically close have a higher degree of DNA sequence similarity
than organisms that are phylogenetically distant. Further evidence for
common descent comes from genetic detritus such as pseudogenes,
regions of DNA that are orthologous to a gene in a related organism,
but are no longer active and appear to be undergoing a steady process
of degeneration from cumulative mutations. Fossils are important for
estimating when various lineages developed in geologic time. As
fossilization is an uncommon occurrence, usually requiring hard body
parts and death near a site where sediments are being deposited, the
fossil record only provides sparse and intermittent information about
the evolution of life. Evidence of organisms prior to the development
of hard body parts such as shells, bones and teeth is especially
scarce, but exists in the form of ancient microfossils, as well as
impressions of various soft-bodied organisms. The comparative study of
the anatomy of groups of animals shows structural features that are
fundamentally similar or homologous, demonstrating phylogenetic and
ancestral relationships with other organisms, most especially when
compared with fossils of ancient extinct organisms. Vestigial
structures and comparisons in embryonic development are largely a
contributing factor in anatomical resemblance in concordance with
common descent. Since metabolic processes do not leave fossils,
research into the evolution of the basic cellular processes is done
largely by comparison of existing organisms' physiology and
biochemistry. Many lineages diverged at different stages of
development, so it is possible to determine when certain metabolic
processes appeared by comparing the traits of the descendants of a
common ancestor. Universal biochemical organization and molecular
variance patterns in all organisms also show a direct correlation with
common descent. Further evidence comes from the field of biogeography
because evolution with common descent provides the best and most
thorough explanation for a variety of facts concerning the
geographical distribution of plants and animals across the world. This
is especially obvious in the field of island biogeography. Combined
with the theory of plate tectonics common descent provides a way to
combine facts about the current distribution of species with evidence
from the fossil record to provide a logically consistent explanation
of how the distribution of living organisms has changed over time. The
development and spread of antibiotic resistant bacteria, like the
spread of pesticide resistant forms of plants and insects provides
evidence that evolution due to natural selection is an ongoing process
in the natural world. Alongside this, are observed instances of the
separation of populations of species into sets of new species
(speciation). Speciation has been observed directly and indirectly in
the lab and in nature. Multiple forms of such have been described and
documented as examples for individual modes of speciation. Evidence of
evolution is available for us to witness in the here and now, here are
my favorite top five: 1) As the huge array of drug resistant pathogens
grows we are learning that evolution is easiest to observe in species
with a quick generation turnover. Since 1988, in the lab of Richard
Lenski, the evolution of twelve E. coli populations from a single
ancestor strain has been studied. Since then, over 50,000 generations
of E. coli have been and gone, and the differences between the
populations and each population from the ancestor strain have been
documented. With samples of each population taken regularly the
accumulated genetic changes can be followed with ease. Over time the
bacteria have become far more efficient at growing under the
conditions used. This study has provided evidence of how evolution
actually occurs. One of the populations developed the ability to
utilize citrate as a nutrient, something otherwise unknown in E. coli
under similar conditions. 2) Studying evolution can take decades, but
occasionally change happens incredibly rapidly. The Blue Moon
Butterfly (Hypolimnas bolina) of the Samoan islands was being attacked
by a parasite which destroyed male embryos. This led to a gender
imbalance whereby males made up only 1% of the butterfly population.
However, within ten generations (~1 year) males had returned to 40% of
the population. This is not because the parasite has disappeared, it
is still present, but it is no longer deadly to male embryos. This
case shows how a mutation giving an advantage can rapidly spread
throughout a population. Any male with the ability to survive
infection would be able to mate with a great many females, due to the
paucity of other males, and spread his immunity through the gene pool.
3) The medium ground finch was well established on the isle of Daphne,
and had been studied in depth. Its beak was suited perfectly for
cracking large nuts. In 1982, the large ground finch from a
neighboring island arrived. These larger finches could drive away the
native medium ground finches and would eat all the large nuts. Over
the period of study, the medium ground finches of Daphne island were
found to have developed smaller beaks more suited to the smaller nuts,
ignored by the invading larger finches. This is a classic study in
evolutionary biology. 4) In 1971, ten Italian wall lizards (Podarcis
sicula) were introduced to the island of Pod Mrčaru from a neighboring
island. The lizards were left for decades, and compared to the colony
from which they were taken. The wall lizards on Pod Mrčaru, having
passed through a tiny genetic bottleneck, were found to have thrived
and adapted to their new island. They were found to have shifted from
a mainly insectivorous diet to one heavy in vegetation. This diet
change seems to have driven dramatic changes in the lizards. The head
of the Pod Mrčaru lizards is larger, and has a far greater bite force.
These are key adaptations for dealing with chewing leaves. The most
exciting sign of evolution is the development of cecal valves, muscles
used to separate portions of the intestine. These serve to slow the
passage of food through the intestine and give time for the bacteria
in the gut to breakdown the plant matter for absorption. This is an
entirely novel development in the Italian wall lizard, and a major
adaptation. 5) The example of the peppered moth is a nice one for
textbooks because it uses a single trait. Speciation involves many
mutations leading to significant changes. The yellow bellied
three-toed skink (Saiphos equalis) is a lizard of New South Wales, in
Australia, that appears to be undergoing the change from laying eggs
to live birth. Since these skinks can either lay eggs or give birth,
it gives scientists the chance to study the adaptations necessary for
live birth. Skink embryos encased in an egg have an extra source of
calcium that the live born skinks lack. It turns out that this
nutritional difference is made up by the mother secreting extra
calcium for the young held inside her. This looks like the first step
on the road to developing a system like the mammalian placenta. Skinks
living on the coast tend to lay eggs, probably because the warm
weather is predictable and sufficient for embryonic development. Those
skinks living in the cooler mountains tend to give birth to live
young, the mother's body providing a more stable temperature. It is to
be predicted that these two populations will at some point separate
into different species as each population becomes fixed in its
reproductive strategy. This brings up a common question in
creationists – If man evolved from apes, why are there still apes?
Well, with the skinks we would see two species formed, an egg laying
and a live birthing species. Each would be best suited for their
habitat. If live birthing skinks evolved from egg layers, why are
there still egg layers? Because each is adapted for its niche.

GoodWithoutgod, 1 hr ago

Our distant ancestors seemed to have had significantly better teeth
than us and not a dentist nor toothbrush in sight.

Ryker, 2 hrs ago

Where's Preachy and Frosty?

Edward, 1 hr ago

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