Addomesticamento del Micio: indizi dal Genoma.

Genome reveals clues to cat domestication 

 Cats and humans have shared the same households for at least 9,000 years, but we still know very little about how our feline friends became domesticated. 
An analysis of the cat genome led by researchers at Washington University School of Medicine in St. Louis reveals some surprising clues. 

Researchers at Washington University School of Medicine in St. Louis led an international  team that sequenced and analyzed the cat genome to better understand the animal's  domestication. Pictured is a blue Abyssinian [Credit: WikiCommons] 

Cats have a relatively recent history of domestication compared with dogs; canines arose from wolves over 30,000 years ago. 
"Cats, unlike dogs, are really only semidomesticated," said senior author Wes Warren, PhD, associate professor of genetics at The Genome Institute at Washington University. "They only recently split off from wild cats, and some even still breed with their wild relatives. So we were surprised to find DNA evidence of their domestication." 
One way scientists can understand the genetics of domestication is to look at what parts of the genome are altered in response to living together with humans, Warren added.

The researchers compared the genomes of domestic cats and wild cats, finding specific regions of the domestic cat genome that differed significantly. 
The scientists found changes in the domestic cat's genes that other studies have shown are involved in behaviors such as memory, fear and reward-seeking. 
These types of behaviors -- particularly those when an animal seeks a reward -- generally are thought to be important in the domestication process. 

"Humans most likely welcomed cats because they controlled rodents that consumed their grain harvests," said Warren. "We hypothesized that humans would offer cats food as a reward to stick around." 
This meant that certain cats that would normally prefer to lead solitary lives in the wild had an additional incentive to stay with humans. 
Over time, humans preferred to keep cats that were more docile. 

Cat genome project 
The cat genome sequencing project, funded by the National Human Genome Research Institute, part of the National Institutes of Health (NIH), began in 2007.
 The project's initial goal was to study hereditary diseases in domestic cats, which are similar in some cases to those that afflict humans, including neurological disorders, and infectious and metabolic diseases. 
To obtain the high-quality reference genome needed for this research, the team sequenced a domestic female Abyssinian cat named Cinnamon. 
They chose this particular cat because they could trace its lineage back several generations. This cat's family also had a particular degenerative eye disorder the researchers wanted to study. 
To better understand characteristics of domestication, the researchers sequenced the genomes of select purebred domestic cats.

Hallmarks of their domestication include features such as hair color, texture and patterns, as well as facial structure and how docile a cat is. 
Cats are bred for many of these types of characteristics. 
In fact, most modern breeds are the result of humans breeding cats for their favorite hair patterns. 
The team also looked at a breed called Birman, which has characteristic white paws. The researchers traced the white pattern to just two small changes in a gene associated with hair color. 
They found that this genetic signature appears in all Birmans, likely showing that humans selectively bred these cats for their white paws and that the change to their genome happened in a remarkably short period of time. 
The group also compared the cat genome with those of other mammals -- including a tiger, cow, dog and human -- to understand more about the genetics of cat biology. 
"We looked at the underlying genetics to understand why certain abilities to survive in the wild evolved in cats and other carnivores," said Michael Montague, PhD, the study's first author and a postdoctoral research associate at The Genome Institute.
 The differences they found in the cat genome help explain characteristics such as why cats are almost exclusively carnivorous and how their vision and sense of smell differ from other animals like dogs.

Solitary carnivores 
To digest their fatty, meat-heavy meals, cats need genes to efficiently break down fats. The team found particular fat-metabolizing genes in carnivores such as cats and tigers that changed faster than can be explained by chance. 
This more rapid change generally means these genes provide some sort of digestive advantage to carnivores that only consume animal proteins. 
The researchers did not find such changes in the same genes of the cow and human, who eat more varied diets and would not need such enhancements. 
Cats also rely less on smell to hunt than dogs.

So it is not surprising that the researchers found fewer genes for smell in cats than dogs.

 But they did find more genes related to an alternate form of smell that detects chemicals called pheromones, which allow cats to monitor their social environment, including seeking out the opposite sex. 
This ability is not as important to dogs, which tend to travel in packs. 

But it is crucial in cats, which are more solitary and may have more difficulty finding mates. 
Cats also have better hearing than most other carnivores, including an ability to hear in the ultrasonic range to better track prey. 
Their vision is also exceptional in low light. 
"Cats tend to be more active at dawn and dusk," said Montague, "so they need to be able to detect movement in low light." 
Accordingly, the team identified specific genes that likely evolved to expand cats' hearing range and their vision in low light. 
Even though the genomes of domestic cats have changed little since their split from wild cats, the new work shows that it is still possible to see evidence of the species' more recent domestication. 
"Using advanced genome sequencing technology, we were able to shed light on the genetic signatures of cats' unique biology and survival skills," said Warren. "And we were able to significantly jump start our knowledge about the evolution of cat domestication." 

The research appears Nov. 10 in the Proceedings of the National Academy of Sciences Early Edition. 


Author: Gaia Remerowski 


| Source: Washington University in St. Louis [November 10, 2014]

DNA umano, 400.000 anni fa

Questo è un articolo interessante: esso getta nuova luce sulla linea dell'uomo di Denisova (che era strettamente imparentato con il Neanderthal ed apparve in Europa  MedioOrientale, ma evidentemente si estese fino all'Europa dell'Ovest!) e mostra che - con ogni probabilità - il DNA del Neanderthal apparve ben prima di quanto prima si supponeva, in Europa, anche se la data resta approssimata e da stabilire.

Gli ominini trovati nel nord della Spagna (Sima de los Huesos, vedi articolo) si raggruppano geneticamente con i Denisova (un mtDna, quindi una donna).  La figura, che illustra il nuovo albero filogenetico che ne deriva è estremamente descrittiva...

400 thousand year old 

human mtDNA 

from 

Sima de los Huesos

It will come to no surprise to people who noticed an earlier paper on cave bear mtDNA from Atapuerca that the folks at the Max Planck Institute would try to do the same for the plentiful human remains found in the Pit of Bones.

A new paper in Nature reports their success, and overnight increases by an order of magnitude the time depth for which we now have human mtDNA from what is commonly designated as Homo heidelbergensis, from right in the middle of the Middle Pleistocene. Obviously, this opens new vistas for archaeogenetic research, making it possible to directly look at early pre-sapiens forms of humans, and not only on their final forms prior to their replacement, the Neandertals and Denisovans.

The most impressive aspect of the new paper is most likely the technical challenges that the researchers must've overcome to achieve this result. The cave bear DNA showed that this was possible, but human DNA adds an additional complication in the form of contamination by a closely related species, us.

But, the new evolutionary result which will interest those of us not interested in the minutiae of biomolecules will no doubt be the fact that the Sima hominin's mtDNA formed a clade with the much more recent Denisova girl.

Until now, we knew that Neandertal mtDNA grouped together and so did modern human mtDNA. The two groups shared a Middle Pleistocene common ancestor and a much more distant common ancestor (~1 million years) with the mtDNA found in Denisova. The new Sima specimen shares descent from Denisova. This is important because it shows that whatever archaic human population the Denisovan mtDNA belonged to also extended to western Europe. And, surprisingly, the Sima specimen did not group with Neandertals, as might be expected because of the incipient Neanderthaloid morphology of the Sima hominins which has been a matter of controversy as it pushes back the evolutionary lineage of H. neandertalensis deeper into the Middle Pleistocene that some researchers accept.

Before this paper, it was believed that H. heidelbergensis evolved somewhere (perhaps Near East or Africa), a subset of it evolved to H. sapiens in Africa, and a different subset evolved in Eurasia, leading up to H. neandertalensis in the west, and unknown forms in the east, of which the Denisova girl was a matrilineal descendant. The next question is: when did Neandertals and Neandertal mtDNA appear in Europe? 

It can now be hoped that such questions will be answered directly. The Sima individual studied in this paper is not some frozen specimen from the Arctic, preserved by a freak accident in pristine form for hundreds of thousands of years, but a person who lived in Southwestern Europe. I am fairly sure that this won't be the last really old human we see a paper about in the coming years. Human mtDNA used to present a simple picture at the time of the discovery of African mitochondrial Eve: the deepest splits were in Africa and Eurasians belonged to a subset of African variation. But, as more and more archaic Eurasian mtDNA is sampled, it now appears that modern human mtDNA is a subset of world human mtDNA whose deepest splits are in Eurasia, and the next deepest splits are in Africa. Obviously, this may be a consequence of the fact that archaic human mtDNA has only been sampled from Eurasia, for factors relating to DNA preservation. But, it is nonetheless interesting to wonder where on the tree the mtDNA of archaic Africans would fall.

Nature (2013) doi:10.1038/nature12788

A mitochondrial genome sequence of a hominin from Sima de los Huesos 

Matthias Meyer et al.

Excavations of a complex of caves in the Sierra de Atapuerca in northern Spain have unearthed hominin fossils that range in age from the early Pleistocene to the Holocene1. One of these sites, the ‘Sima de los Huesos’ (‘pit of bones’), has yielded the world’s largest assemblage of Middle Pleistocene hominin fossils, consisting of at least 28 individuals dated to over 300,000 years ago. The skeletal remains share a number of morphological features with fossils classified as Homo heidelbergensis and also display distinct Neanderthal-derived traits. Here we determine an almost complete mitochondrial genome sequence of a hominin from Sima de los Huesos and show that it is closely related to the lineage leading to mitochondrial genomes of Denisovans, an eastern Eurasian sister group to Neanderthals. Our results pave the way for DNA research on hominins from the Middle Pleistocene.

Link