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They are the epitome of survival against the odds, enduring some of the most hostile weather conditions on the planet on a continent that is almost completely barren. 

Now scientists have gained a valuable insight into how penguins are able to cope with the extreme cold, high winds and months of darkness they experience in Antarctica.

Genetic analysis of the genomes of two species of penguin - emperor penguins, the largest of the family, and their smaller cousins Adélie penguins - has revealed some of their secrets to survival.

Adélie penguins have eight genes for metabolising fat, which may allow them to adapt quickly to warmer conditions but could leave them struggling in colder weather when food sources are more scarce

Researchers found that the penguins have a vast number of genes responsible for creating the raw material needed for feathers - proteins known as beta-keratins.

They carry more genes for a particular type of beta keratin than any other bird and it is thought this is what allows them develop their thick plumage of short, stiff feathers that keep them warm.

The densely packed and barbed feathers also trap air to keep them buoyant and remain waterproof while they are swimming, allowing them to reach speeds of up to 22 mph in some species.

The scientists also discovered that penguins have a gene called DSG1, which in humans is known to be involved in a dermatological disease characterised by thick skin on the palms and feet.

It believe these genes may help the penguins develop a uniquely thick skin compared to other birds.

The DNA analysis also revealed that these two species of penguin have very different mechanisms for storing fat, which helps insulate them from the cold and survive long periods without eating.

Male emperor penguins can survive for up to four months without food while incubating their eggs from the Antarctic storms as the females forage out at sea for fish.

The researchers found three key genes that they believe may help them to store fat. 

However, Adélie penguins have eight genes involved in metabolising fat, which may explain why they have been able to adapt more quickly to changes in climate.

Professor Guojie Zhang, associate director of the China National Genebank in Shenzhen, who oversaw the study, said: 'Penguins show distinct evolution relative to other bird species. 

'They can't fly, have specialized skin and feathers, degenerated wings, and live in a cold environment in which most other birds could not survive. 

'Comparative genomics is a powerful tool for providing answers on the molecular basis of these evolutionary changes and how organisms deal with the conditions they are exposed to. 

'Our study has revealed several of these secrets for the two penguins.

'The expansion of keratinocyte β-keratin genes and the positive selection on EVPL and DSG1 may have contributed to generating the unique skin and feathers in penguins.' 

Researchers took blood samples from Adélie penguins (pictured) on Inexpressible Island in Antarctica

Emperor penguins endure some of the coldest conditions on Earth as they incubate their eggs through the Antarctic winter, but they have unique genes for storing fat and growing dense plumage to keep warm

The researchers, whose work is published in the journal GigaScience, analysed the DNA of a male emperor penguin found on Emperor Island, near Zhongshan Station in east Antarctica and a male Adélie from Inexpressible Island in the Ross Sea of Antarctica.

They were conducting their study as part of the Avian Phylogenomics Project, which is aimed at unraveling the avian tree of life.

The genetic research showed that penguins first appeared on Earth around 60 million years ago. Emperor and Adélie penguins evolved from a common ancestor around 23 million years ago.

The study also showed that the Adélie penguin population increased rapidly about 150,000 years ago when the climate became warmer, but later declined by 40% about 60,000 years ago, when the weather became colder and drier.

In contrast, the emperor penguin population remained stable, suggesting that they were better adapted to glacial conditions.

The study has also helped to shed light on the evolution of penguins' short wings which they use to 'fly' through the water rather than the air like their avian cousins.

The scientists found 17 genes in the penguin genomes taht had unique changes, with one in particular, called EVC, showing a large number of genetic changes compared to other birds.

Mutations in EVC2 in humans are known to cause Ellis-van Creveld syndrom, which causes sufferers to have short-limb dwarfism and short ribs.

It is possible that changes in this gene is what caused the stubby wings in penguins.

Emperor penguins can go without food for upto four months while waiting for their chicks to hatch, which requires them to have specially adapted metabolisms for storing and using fat through in the cold winter

Adélie and emperor penguins have adapted to the low light conditions they endure during the Antarctic winter

Penguins aquatic lifestyle and the long periods of darkness during the Antarctic winter have also taken their toll on the penguins eyesight.

The scientists compared the penguin genome to 48 other bird species. They found that while most birds had four classes of genes for photosensitive proteins in their cone cells of their eyes, Adélie and emperor penguins had just three.

It is possible the penguins lost the need for these proteins in their eyes due to the poor light quality they experience.

However, emperor penguins, which breed in the winter, had extra genes that are thought to improve the activity of their rod cells - the retinal cells that detect low levels of light - while Adélie, which breed in the spring and summer, did not have these.

Professor Zhang added: 'Morphological changes in the epidermis and forelimbs are critical for underwater flight in penguins, so the candidate genes that we discovered in this study are highly valuable for future functional studies.

'The genes involved in light transduction and lipid metabolism exhibit signals of positive selection or pseudogenization in penguins, suggesting their evolutionary responses to the extreme conditions of light and temperature in Antarctica.'

The genetic studies will help scientists understand how penguins will adapt to future changes in the climate

However, the findings could also help scientists predict how the penguins will be able to adapt to changing climate conditions in the future.

Dr Cai Li, team lead at the Beijing Genomics Institute in Shenzhen, China, said: 'These different patterns in historical population change also suggest that future climate change may have impacts on the two penguin species. 

'For example, the fact that emperor penguins didn't experience the same population boom as Adélie penguins in warm climates means that they could suffer more from global warming, and this needs to be considered in conservation efforts in Antarctica.' 

Professor David Lambert, an evolutionary biologist who also took part in the study at Griffith University, Australia, added: 'Although Adélie and Emperor penguins both breed on the Antarctic continent, they do so in very different ways.

'By sequencing the genomes of two penguin species we have been able to compare many of the genes that are responsible for these different abilities to do the same thing - namely to survive and breed in Antarctica. 

'This study is particularly important because it now provides us with the opportunity to conduct large scale evolutionary studies of both species.'