BELLE ISLE, Mich. (FOX 2) - The giant slide may not be the most dangerous thing on Belle Isle. People only need to look at the tree standing in its shadow. Protruding out of its trunk is a living reminder of the beasts that roamed North America and the legacy they left behind.

Scientists call them evolutionary anachronisms. But to the visitors of Belle Isle, they're giant thorns.Unlike the finger-sized spikes that grow on rose bushes, these thorns can grow more than half a foot long. If thorns are meant to be a defense mechanism to keep away predators, what animal is big enough to require barbs that could impale someone?

The answer lies in the past. A honey locust's thorns are too big to fend off nesting birds or a curious deer's snout. But if an elephant-sized animal wanted to knock over the tree, the thorns would be perfectly suited to ward off its advances. Elephants aren't native to North America, but furry mammoths and tusk-wielding mastodons once walked the land, which is where this story begins.

"Go back only 9,000 to 13,000 years ago, the landscape had a lot of megafauna, including mammoths and mastodons, giant sloths; we had giant beavers, camel-like animals and horses," said Dr. Christopher Dick at the University of Michigan Herbarium. 

Those species disappeared with the arrival of humans in North America and the end of the last ice age. Scientists know they lived in Michigan, having found the bones of woolly mammoths in a soybean field in 2015. But in the millions of years leading up to their demise, plants and trees coexisted alongside these ancient beasts - and even used them to spread across the continent. Evolution helped pick out the traits that helped them best survive, which included using animals to disperse their seeds - while deploying defenses to protect them in the process.

Honey locust trees like the one growing on Belle Isle with its terrifying thorn clusters may be the best example of this relationship. Southeast Michigan is actually the most-northern region where honey locust trees grow. Their distribution spans both sides of the Mississippi River and stretches all the way down to Louisiana. People have also done their fair share of planting honey locust trees because of their hardiness in tough environments, choosing to grow them in cities. These variations have been cultivated to grow without the thorns that natural honey locust trees still produce.