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Fossils from Our Past Caution Us on Our Path Towards the Future

By Shaquille Jones

Before the arrival of humans, the Bahamian landscape resembled a mysterious, spellbinding wonderland dominated by glorious creatures and lush, tropical forests. Crocodiles, maliciously referred to as “serpents” by Christopher Columbus, sat on the throne of this picturesque kingdom and instilled fear with their menacing stares and powerful bites.

Scientists have theorized that Cuban crocodiles, extinct in The Bahamas today, may have migrated from Cuba when a period of low sea levels exposed a much larger area of the Bahama banks or may have even originated in our island chain. Further examination of their ancient DNA will help scientists to better understand the origin and migratory patterns of this species.

Owls observed closely as oblivious tortoises made the fatal mistake of finding refuge in caves in order to regulate their body temperature or more simply, to obtain their much-needed beauty sleep. Lurking nearby, hungry crocodiles gobbled these innocent and startled souls.

Little did these species know, a group of invaders would appear from the aquamarine horizon and eventually conquer the food chain, forever changing their once pristine ecosystem.  All that remains of these animals are hollow bones that eagerly await those brave enough to disturb their dark, isolated graves.

Through the study of isotopes and ancient DNA, scientists are now able to give these fossils the opportunity to tell their stories and hopefully, we are wise enough to listen.

Sinkholes are burial chambers of secrets that owe their existence to the calcium carbonate (limestone) geology of The Bahamas. Thousands of years ago, when sea levels were much lower, rain permeated the porous limestone terrain and slowly dissolved the bedrock, which resulted in numerous sinkholes and caves being carved into the landscape.

After the ice age, when sea levels began to rise, anoxic sea water seeped through their eerie systems of tunnels. These water-filled cavities are known as blue holes.

A notable feature of blue holes is a murky layer of water located between lighter, oxygenated fresh water and the deeper, less dense, oxygen-deficient sea water. This potentially deadly zone is called a halocline and often contains hydrogen sulfide –a poisonous gas that is discharged from moderately decomposed plant material called peat. It is this unique water chemistry that is responsible for preserving the well-hidden treasures that scientists are now discovering.

The study of isotopes has undoubtedly been the key to unlocking the chilling secrets of fossils found within Bahamian sinkholes.

In simple terms, isotopes are atoms that contain the same number of protons (positive charge), but differ in the number of neutrons (no charge). An isotope is said to be unstable if its nucleus experiences impulsive decay which produces radioactive energy. Radiocarbon dating, a process that examines unstable carbon isotopes, is employed to determine the age of objects that contain organic material and is often cited as one of the most celebrated tools in modern science.

Archaeologists, for example, are now better equipped to positively identify skeletal remains due to this miraculous scientific breakthrough. Stable isotopes, however, do not undergo spontaneous nuclear decay or emit radioactive energy. Scientists often analyze stable carbon and nitrogen isotopes in order to comprehend the diet of organisms. For instance, they can tell whether someone’s diet consists of healthy food or if most of their lunch is spent consuming greasy cheese burgers and salt-laden fries.  You are what you eat!

Isotopic analysis of fossils found in sinkholes has painted a considerably clearer portrait of the sudden event that drastically altered the Bahamian ecosystem. Through radiocarbon dating, scientists have discovered that the extinction of crocodiles and tortoises in The Bahamas coincides with the arrival of the Lucayan people, and this fact highly implicates humans in their tragic and untimely demise.

Because of the high prevalence of crocodile bite marks found on tortoise shells throughout The Bahamas, scientists have concluded that crocodiles were their primary predators and it is conceivable that the stark decline of tortoises had a significant impact on the ecosystem.

Tortoises fed mainly fed on terrestrial plants, according to Nancy Albury, project coordinator and paleontologist at the National Museum of The Bahamas. On Crooked Island, strong trade winds shower copious amounts of sea water spray onto the coastal vegetation, resulting in the isotopes of tortoises discovered there having a slightly higher marine composition than those found in the northern Bahamas.

Numerous plants in the ecosystem relied on tortoises for more efficient germination, as they often cropped the under growth and passed seeds after digestion. Once abundant, their population unsurprisingly dwindled during the same period as the appearance of Lucayans who relied in part on terrestrial fauna for their diet. This decline had a detrimental effect on both the vegetation and food web of the islands.

According to scientists, overhunting by the Lucayan people is the primary reason for the devastating and widespread loss of animal species during this time period. Settlements were frequently established in areas that provided ample opportunities for hunting. Furthermore, dangerous storms often hindered marine navigation, and research shows that approximately half of the Lucayan people’s diet was terrestrial and half was marine based.

The Lucayans, assuming that fishing was too perilous during heavy rain and rough seas, turned to inland hunting and this proved to be of fatal consequence to Bahamian reptilian populations. Tortoises were heavily hunted due to their large size, their slow-moving pace, their ample population and their desirability as captive animals. Due to the fact that tortoises can survive for weeks without food and water, they were most likely captured and kept alive by Lucayans in order to provide protein for long periods.

Essentially, they were the canned food of the time.

But as their population decreased, crocodiles grew increasingly hungry and stalked humans, whom they viewed as vulnerable prey. Lucayans proceeded to hunt them to the point of extinction in a frenetic attempt to prevent casualties. The steep reduction of Bahamian iguana populations is also widely attributed to overhunting by the Lucayans.

Some anthropologists believe that destructive Lucayan agricultural practices may have played a prominent role in the extinction of many species that no longer exist in The Bahamas. Slash and burn, sometimes referred to as shifting cultivation, is a land clearing process that is still practiced in some areas of the sparsely populated, less industrialized southern Bahamas and entails burning extensive areas of forest for crop land. Subsistence farmers, Lucayan families often utilized slash and burn fields until the soils were no longer viable due to the exhaustion of nutrients.

Not only does this practice reduce the potential yield of the land, but it also results in widespread environmental degradation and habitat loss for various species. Unable to adapt to this drastic change in their ecosystem, various animals sadly perished but now, they are speaking from beyond the grave and their tales of caution echo throughout the nation.

Research conducted on Bahamian sinkholes paints the story of an idyllic paradise that has been irreversibly blemished through years of human activity. It also unquestionably illustrates the hazards that arise from disrupting the ecosystem’s fragile food web. In contemporary times, economic activities such as illegal fishing and dredging have destroyed coral reefs and mangrove forests, making The Bahamas more susceptible to the devastating effects of storm surge.

On the bright side, various Bahamian organizations are leading the charge in making sure that future generations are able to enjoy the splendid beauty of our islands. Friends of The Environment, a local non- profit, is one such organization that is devoted to educating the public about the detrimental ways in which garbage and trash pollutes our water supply, and can suffocate animals such as sea turtles. Without a doubt, it is imperative that we fully understand the crucial role that humans play in our ecosystem as our survival depends on it.

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