"This is Florida  a taste of the tropical  one of the world's most popular holiday destinations." "Here, mankind's unquenchable desire to explore and colonize reaches astronomical proportions." "And yet we are relative newcomers here." "While other creatures roamed this part of North America for hundreds of millennia, we only arrived at the end of the last great ice age," "13,000 years ago." "For most of its existence," "North America remained untouched by humans... its dramatic landscapes and wildlife undisturbed." "Then, sometime around 13,000 years ago, just as the ice started to relax its grip, hunters from the north set foot in Florida for the first time." "Imagine if we could go back and join them as they explore this unknown land  encountering strange animals not seen before by human eyes." "By piecing together the evidence these creatures left behind, we can build a picture of this sub tropical corner of the continent as it was 13,000 years ago." "While most of North America was still in the grip of the big freeze," "Florida was an ice age oasis." "Florida is aptly named the Sunshine State." "With an average of 8 hours of sun a day, it seems a world away from any ice age." "Even 13,000 years ago, the massive ice sheets were hundreds of miles away to the north." "So what was it like back then?" "To investigate Florida's ice age past, one of the best places to look is underground   and underwater." "Just below the surface lies a very strange world." "Millions of years of water action has dissolved the limestone rock, forming a system of flooded caves and tunnels." "This vast underground network runs for thousands of miles." "Much of Florida is basically a big rock honeycomb." "ln places the water is forced to the surface,forming springs." "Florida has one of the largest concentrations of springs in the world." "Filtered through sand and rock, the water is crystal clear." "And welling up from deep within the earth, it is a constant 22 degrees Centigrade" "This creates steaming oases, and a profusion of life." "Today these warm springs are a refuge for one of Florida's most tropical inhabitants." "The West Indian manatee wasn't present during the last ice age, but returned here as the waters warmed up." "Even now it is only found around this sub tropical tip of the continent." "But these springs aren't just a haven for modern day wildlife they've also yielded many secrets of the distant past." "When these pools were first explored, they would have looked like this... strewn with astonishing fossil remains from ice age beasts." "Florida has one of the richest fossil records of the ice age anywhere on earth." "So what kind of creatures did such bones and skulls belong to, and how did these springs become their graveyards?" "Many of the fossils are from animals that you can still see today   indeed we'd recognise the vast majority of Florida's ice age wildlife." "Nevertheless the most spectacular ice age beasts did become extinct." "And remarkably some of them share a common ancestor with modern manatees." "At first sight manatees might look like seals or dolphins, but in fact some of their closest relatives live on land..." "These toenails are the giveaway remarkably similar to those of elephants." "13,000 years ago, two other members of the elephant family roamed this land." "The manatees that swim in Florida's springs today are living relatives of ice age mammoths and mastodons." "Some of the bones found in these springs are easy to identify, but scattered in among them are some more obscure remains." "What kind of animal could this belong to?" "These rosettes are bony scales, or 'scutes', similar to those that cover some reptiles today." "But this is only one piece of the jigsaw." "Imagine what the creature would have looked like when all these pieces were fitted together." "The scutes - around 2000 of them once formed the shell of a huge animal called a Glyptodont." "With its heavyweight exterior the glyptodont looks like a reptile... like the alligator, which has been around for millions of years long before the last ice age." "But the glyptodont wasn't a reptile so what was it?" "There is a relative of the glyptodont that's still alive today." "It's the Armadillo, and it's a mammal the only mammal with this kind of armour in the whole of North America." "It may give us some idea of how an ice age glyptodont might have looked when alive." "Armadillos have poor eyesight, and rely mostly on their sense of smell." "Much of their time is spent nose to the ground in search of food." "Like the glyptodont, they're covered in a layer of bony scutes." "But the armadillo's body armour is surprisingly thin and flexible and doesn't slow its owner down." "So what about the glyptodont?" "The glyptodont's scute casing was up to 5 centimetres thick, and fused into a solid shell." "The shell alone was extremely heavy... and the entire animal probably weighed as much as a small car." "It had extremely sturdy legs and five toes on each foot to spread its massive weight." "The heavy tail probably acted as a counter balance." "So the glyptodont wasn't built for speed, but inside all this body armour, you'd imagine it was well protected." "But one fossil skull tells a different story." "It suggests the glyptodont's defences weren't impenetrable." "These holes are the unmistakable hallmark of a violent death." "Their shape suggests that they were made by the teeth of a big cat... ... but which one?" "Today there's only one large cat in the region... the Florida panther." "Though similar to the cougar of the western states, it's now much rarer." "But it was around during the ice age, so could it have killed the glyptodont?" "Although it could easily manage a deer, the Florida panther was probably too small to tackle such a giant." "But it wasn't the only big cat around 13,000 years ago." "There was also the mighty American lion" "... powerful enough to kill a glyptodont." "The Scimitar-Toothed Cat known to attack young Mammoths was also big and strong enough." "And then there was the most infamous cat of all the Sabre-Tooth." "Like the scimitar, it saved its awesome fangs for slashing soft flesh." "It would have been unlikely to risk breaking them on bony armour." "But the warm climate of ice age Florida made it a sanctuary for another killer cat." "Still South America's top predator, the jaguar is capable of taking prey much larger than itself." "Weight for weight, it's probably the most powerful cat alive today." "But most significant of all, the jaguar has a tell- tale trademark." "Instead of going for the neck or snout like most cats do, it kills with a crushing bite through the skull into the brain." "This makes the jaguar prime suspect in this case." "Even the glyptodont's defences had a fatal flaw." "13,000 years ago another, very different kind of hunter reached this warm corner of the continent." "Florida's springs have produced an unparalleled record of these first people... examples of their craftsmanship and hunting expertise, including razor sharp flint spear points..." "The area was rich in flint for making weapons, and in animals to hunt." "And with the milder climate, these people probably had an easier life than their contemporaries further north." "Small clues to their arrival have survived undamaged over 13,000 years..." "Spear points, fishhooks and other glimpses of their daily life, showing the versatility of these first inhabitants of the sunshine state." "They hunted a wide range of ice age animals, and Florida possesses a unique record of one such encounter." "The skull of an extinct bison, restored here, was discovered in one of the rivers." "Planted deep in the top of the skull was a flint spear-point." "But how did one man and a spear produce the huge force behind this blow?" "The answer lies with small bits of ivory, like this." "They were once part of an 'atlatal' or spear thrower." "An atlatal acts as a sort of catapult, magnifying the strength of a hunter's throw, allowing him to launch a spear up to 200 metres" "with enough power to drive the point through a bison's skull." "It's this kind of sophisticated technology that helped these early North Americans to spread throughout the entire continent." "But what else did they find once they reached Florida?" "Florida's ice age wildlife was remarkably rich and diverse." "There were many familiar animals normally found further north, but also creatures unique to the tropics." "The result was a mixture of species unlike anything we see today... and an abundant food source for the human immigrants." "So what produced ice age Florida's wealth of wildlife?" "Part of the answer comes from the ice itself." "At the peak of the last ice age, massive glaciers up to 2 miles thick covered over half the North American continent." "The ice destroyed the habitat over which it lay, but it also had a profound impact on regions far away." "It created a domino effect that rippled down the continent." "The cold-climate conifer forests of the north displaced broadleaved woodlands." "Plants and animals were gradually pushed south to find a warmer climate." "Florida became a refuge from the cold." "Down here is where the ice age north met the sub-tropical south." "Today in a cool, wooded part of the sunshine state, you can still see some of these northern refugees." "The valleys along the Apalachicola River are home to many species that were forced here in the ice age and now remain far away from their main populations further north." "Like the Copperhead snake  and an astonishing variety of amphibians." "During the ice age," "Florida was crucial to the survival of many such mild weather species." "They couldn't have withstood the cold up north, and without this refuge they would simply have become extinct." "Another leftover, but one that arrived from the opposite direction..." "This is the Virginia Opossum... a tree dweller found throughout many of the southern states." "It's the only North American marsupial the young are born premature and nurtured in the mother's pouch." "And its only close relatives today are found in Central and South America." "The opossum is a rare survivor from a South American invasion." "ln the ice age there were many other species that had travelled north to Florida including a giant." "This spectacular claw is 40 centimetres long." "And it belonged to a creature whose fossil remains have been found throughout Florida." "It's the claw from a Giant Ground Sloth." "And it really was a giant," "6 metres long and weighing up to 4 tons, it rivalled the mammoths in size." "Although the giant ground sloth is now extinct, like the opossum, it has family ties in South America." "The family resemblance is easy to see..." "These menacing claws are used as grappling hooks, not weapons..." "They belong to the tree sloth, a peaceful vegetarian that spends its time eating leaves." "It seems a far cry from our vision of an ice age beast." "It's likely giant ground sloths used their claws in a similar way to hook branches and pull them within reach." "Like tree sloths, they were vegetarians, and probably not fussy about what they ate... chewing their way through leaves, fruit, twigs and all." "The big difference between the two is their size." "Giant Ground Sloths were 500 times bigger than their modern relatives   and standing upright on their back legs, they towered as tall as a giraffe." "So far we have pieced together something of the people who first explored the south east of the continent, and the wildlife they must have encountered and hunted." "But what about the climate and the landscape they all lived in?" "Florida is tropical today but how warm was it 13,000 years ago?" "This is Little Salt Spring in central Florida... the source of one of the most unlikely clues to the climate of the past." "Brought up from a ledge more than 20 metres below the surface, was the fossilized shell of a tortoise... a giant tortoise, much like this one." "Giant Tortoises are now only found basking in the heat of a few islands along the equator." "They can grow more than 2 metres long and weigh as much as 3 men." "But the Giant Tortoises of ice age North America were even larger." "Florida does have tortoises today, but on a much smaller scale." "This is the Gopher Tortoise." "Tortoises are cold-blooded animals they rely on external temperature to keep themselves warm." "Although Florida is plenty warm enough for much of the year, during the winter months it can get cold." "So to survive the winter Gopher Tortoises must burrow and hibernate underground." "The colder it gets, the deeper into their burrow they go." "Giant Tortoises, however, can't burrow and they sleep above ground." "They need relatively warm temperatures all year round." "The fact they were in Florida during the ice age means that, paradoxically, the climate must have been more stable and even milder than it is today." "So we know something of the climate but what about the vegetation and the landscape." "How did that look 13,000 years ago?" "Today Florida is one of the wettest parts of the continent, especially the vast swampy area known as the Everglades." "Flooded grassland stretches as far as the eye can see." "But despite their name, the mighty Everglades did not exist during the ice age." "So what did prehistoric Florida look like?" "There's one place in Northern Florida that has revealed more ice age secrets than almost anywhere else  the dark, slow moving waters of the Aucilla River." "Here, ideal conditions for fossilization created a hidden store of ice age evidence." "Unlike in the crystal clear spring waters, these clues were never on view for all to see." "But the Aucilla has now been studied intensively for more than 20 years." "Along some stretches of the riverbed were massive bones, recreated here, perfectly preserved for more than 13,000 years." "One of the most significant discoveries was the huge skull of an American Mastodon." "Mastodons, close relatives of mammoths, were widespread all over North America during the ice age." "They grew over 3 metres tall the size of African Elephants today." "We know a lot about the mastodons, especially their diet, thanks to the preserved dung they left behind." "Some of this ice age dung was found beneath the skull in the Aucilla." "The dung contained plant remains that tell us what the mastodon was browsing on 13,000 years ago or more." "A mixture of trees and grasses." "This suggests that ice age Florida was drier than it is today a mix of woodlands and Savannah, rather than swamps." "And mastodon teeth found in the Aucilla held a more important revelation." "The enamel contains chemical signatures of the local soil, passed via the plants the mastodons ate." "But some of the chemicals found in the Aucilla teeth could only have come from soils hundreds of miles further north." "The inescapable conclusion is that these Mastodons migrated making a round trip of more than 400 miles every year." "And since their dung also contains remains of summer fruits from the Aucilla region, they must have travelled north for the winter." "The question is why?" "Why leave a place, which, as we have seen, was abundant with food, and a refuge from the cold?" "And why go north for the winter, when most migrants move south?" "Perhaps the present climate can provide a clue." "Florida has a peculiar seasonal quirk." "Although the winter months are cooler, they are also drier - much drier." "Between October and February there's almost no rainfall at all." "Could it be that drastic water shortage was the reason for the mastodons' epic migrations?" "Another big piece of this puzzle lies far out to sea..." "This is the ocean floor   but this isn't rock sprouting out of the bottom - it's wood." "It's the remains of prehistoric tree stumps... some dated at more than 12,000 years old." "This sunken forest is unmistakable evidence that what is now seabed was once dry ground." "And what is now Florida's coastline was once many miles inland." "But why?" "To answer that we have to go back to the mighty ice age glaciers that covered almost half the continent." "These glaciers contained immeasurable amounts of ice." "So much water was locked up in this ice that it lowered sea levels by over 70 metres... the south east coastal shelf was exposed and Florida doubled in size... the Everglades were dry land." "This triggered other dramatic changes." "As sea levels dropped, so did the inland water tables." "Florida's fresh water drained away through the porous limestone rock." "Pools dried up and springs diminished." "Florida was on the brink of drought, and animals would have had to travel to find food and water." "So each year mastodons would have migrated to the wetter regions." "But in a few key places, water was still pushed up from underground as a spring  a vital oasis where wildlife would have converged from many miles around." "Many animals would have fed on the surrounding vegetation and others come here to drink." "And predators would have lain in ambush for the unwary." "It's no wonder that so many fossil bones have been found on the bottom of these springs... clues that can open up a window on the ice age past." "Bringing this evidence together, we can create a living picture of this region as it was then." "We can now go back 13,000 years and see what a day around one of Florida's springs might have been like." "Dawn on the southeast tip of ice age North America..." "On the banks of a spring-fed pool, the early grazers stir..." "Today there is a group of larger visitors here too." "A herd of Mastodons, led by the matriarch, have just returned from their annual migration, hundreds of miles to the north." "Now the winter drought is over and the spring water has been topped up by recent rains." "Another group has also set up camp nearby." "Hunters, descendants of the first human settlers that entered the continent in the far north." "Compared to the harsh conditions their ancestors faced, this place is paradise." "Targets for the hunters' spears are plentiful..." "Around the spring, lush vegetation attracts the giant Ground Sloth too..." "Both mastodons and sloths are browsers, but the mastodons roam far and wide to find the kind of plants they need." "The Giant Ground sloth isn't built to travel far, but it makes up for that by having the reach of a giraffe." "lts huge claws may also be used for self- defence... although even the most powerful predator would think twice before tackling so large a prey." "ln any case, this female jaguar is little threat right now..." "Once she's quenched her thirst she'll find a shady place to doze in the heat of the day." "Meanwhile the ground sloth, like the mastodons, must eat most of the day to fuel its huge bulk." "This may be the ice age, but by midday, temperatures soar - drawing another predator to the spring to drink." "The notorious sabre-toothed cat ..." "Most creatures give the Sabre-tooth a wide berth, but this skunk seems unconcerned..." "The sabre-tooth may be the ultimate ice age predator but the skunk is feared too because of its unique system of self-defence." "These stripes serve to warn off most attackers but perhaps the sabre-tooth has yet to learn exactly what they mean." "Stamping his feet, the skunk issues a final warning, but this big cat is still curious... and now the skunk has had enough..." "The dreaded sabre-tooth, killer of mastodons and other ice age giants, is defeated by a small but very smelly skunk." "ln the heat of the day, hunters can afford to slow down and rest in the shade." "It's one of the advantages of a high protein diet." "Llamas originated here in North America and are regular visitors to the spring." "The strange looking tapir is common too." "And there's another animal that is even more bizarre." "A Glyptodont..." "This lumbering vegetarian is no threat to the llamas..." "But it does arouse their curiosity..." "The Glyptodont is shortsighted and wary.." "but it has little to fear from llamas..." "They're easily warned off and soon head back towards the spring." "But as the day cools down, another scent is in the air... alerting the tapir's ultra-sensitive nose to danger." "The llamas pick up the signals too." "It's the jaguar, back on the prowl." "Though very powerful, she's not a sprinter and she needs to get close to her prey before she strikes." "This time she's run too soon and it's a fruitless chase." "Then her attention is diverted... to a slower- moving target." "Slow - but not defenceless... she backs off and tries a different approach." "There's obviously a meal in there, but how to get to it?" "She homes in on the head and bites straight through the skull." "The glyptodont is dead, but the jaguar still goes hungry." "Unable to crack her victim's tough armour, all she manages to walk away with is a bony scute." "The jaguar will vanish from North America, and glyptodonts, like many ice age beasts, become extinct." "But at the bottom of a spring, one tiny fragment of an ice age giant will remain undisturbed for 13,000 years ... while above it the landscape of Florida will change forever." "Next week:" "a giant flood sweeps the northwest." "The predatory scimitar cat battles against the elephant-like mastodon." "And we see how people and giant beasts came together at the edge of the ice."