Tag Archives: Genetics

Remembering Hatuey and the Tainos

 

Cold Malta Hatueys were bountiful at a recent family gathering. As I imbibed one under the tranquil shade of a willow-like tree, its label transfixed me. I slumbered off into childhood memories of the drink. Ahh, mí abuelita (my grandmother). I can still recall the warmth of her gentle smile as she handed Malta Hatuey to me and my cousin. They were tasty rewards for helping her with errands, like running to the local bodega to purchase votive candles. A continuously lit candle adorned the religious shrine that rested on her bedroom’s dresser, brimmed with religious artifacts from rosarios to miniature statutes of La Virgen She prayed for hours to keep all of the family and the world safe.  It was considered a bad omen if a candle wasn’t perpetually lit on her dresser-shrine, as if the extinguishing of its light would allow vile darkness to permeate into our world.

A 1970s photo of my abuelita holding my cousin in the barrio of Newark, NJ. She was a strong woman, both physically and in heart, up to her death at 91.

After remembering my abuelita’s spiritual reflections, I reflected on the bottle of Malta Hatuey in my hand. It’s a sweetened malt beverage of hops and molasses. They are iconic in the Latino community. As a child, I thought the Indian guy depicted on the bottle was the Spanish version of the Lone Ranger’s sidekick, Tonto. But in later life, I learned that Hatuey was a real indigenous chief of our ancestors, the Taínos.

The Taínos are the indigenous people that collectively inhabited the Caribbean islands (Puerto Rico, Bahamas, Dominican Republic, etc) for hundreds of centuries. They were skilled agriculturalists who farmed beans, peppers, corn, yams, and Yuca, a tuber plant that is the source of tapioca, farina, and cassava flour to create breads. As powerful seafarers who built grand canoes, they supplemented their diets with fish and crabs – even eating some of the eggs laid by visiting sea turtles.  Taínos lived in huts constructed from local trees and plant life. They learned how to process the sap of the rubber tree, creating waterproof shoes and ponchos. They created a heavy rubber ball used for a sport, Batey, played on a clay court where two teams (10-30 players per team) would keep it in the air by bouncing the ball with their hips, heads, arms, and legs (no hands). They cultivated cotton to create hammocks and fishing nets. Dance and the sound of drums and maracas pulsated daily life while being enveloped with pristine beaches, soft winds, tropical weather, and green mountainous landscapes. They were peaceful islanders who were one with nature.

A European artist’s depiction of Taíno fishermen. Woodcut from Girolamo Benzoni’s “Historia del Mondo Nuovo,” Venice, 1563.

They were also the first people to greet Columbus. Upon his 1492 arrival, the Taínos greeted and fed them. Columbus noted in his diary that the Taínos were peaceful and beautiful masculine people who would make great slaves. Ultimately, that was the prophetic fate for the Taínos: they were enslaved and forced to work in mines to extract gold for Columbus and his entourage. Bartolome de las Casas–one of the many priests brought in by Columbus–would later write that Columbus’ men made them perform “…tasks utterly beyond their strength, bending them to the earth with crushing burdens, harnessing them to loads which they could not drag, and with fiendish sport and mockery, chopping off their hands and feet, mutilating their bodies in ways which will not bear description.”

A depiction of Christopher Columbus encountering Tainos. An engraving ca. 1594 by Theodor de Bry. It’s important to note that practically every early painting and illustration of Tainos do not reflect them accurately. They are merely artist depictions.

Bartolome was a priest who supported the colonization of the Caribbeans, but after observing the monstrosities inflicted upon the Taínos, he changed his views. Bartolome believed that altruism and spreading the word of God was no longer a driving force in Columbus’ expeditions, but a ruse to fuel the unquenchable appetite for power and gold. He wrote a series of works in the 1550s that outlined the plethora of horrors suffered by the Taínos. He wrote that Columbus’ men would “… breed fierce hunting dogs that would devour an Indian like a hog, at first sight in less than a moment.” Repeated throughout his work are the use of dogs against the Taínos, writing that they purposely kept them hungry to make them more violent. The flesh of Taínos were fed to them.

An early artist’s depiction of Columbus’ dogs feasting on Taínos.

These stories became commonplace as Columbus’ men ventured deeper into the islands, encountering new villages. One village of 2,500 Taínos welcomed them, fed and gave them drinks. Once the feast was over, Columbus’ men turned against them: slashing, disemboweling, and slaughtering them until their blood flowed like a seething river. As Columbus’ men increasingly colonized the islands, their barbarousness deepened. They would bash Taíno babies against rocks or throw them into rivers. They hanged Taínos in groups of 13 and burned them alive – in memory of Jesus and the 12 apostles. For fun, Columbus’ men challenged each other on their skill of cleanly chopping a Taíno’s head off or chopping them vertically in half. In their off time, the rape of Taíno women and young girls was an everyday occurrence. Taíno children young as 9 were sold into the sex trade.

An illustration used in Bartolome de las Casas book depicting the burning of Tainos and a Taino child about to smashed against a wall.

The Taínos did not know what was wrong with these foreign guests. They thought they were mad men who became crazy at the sight of gold. Columbus demanded quotas of gold from each Taíno man (12 and older). When they weren’t met, Columbus’ men would simply chop off their hands. Many Taíno men died within months of working in mines due to over-exertion and extreme malnourishment. Babies died due to lack of milk. Thousands of children died due to hunger, since parents could no longer attend to their crops. Many Taínos would commit suicide instead of becoming slaves. Some would even kill their own children to spare them from the inevitable horrors that awaited their futures.

An artist’s depiction of Columbus’ men chopping off the hands from Taínos for not bringing enough gold. Dogs are feasting on Taínos in the background. Note how some are shown with mutilated noses; this was a common practice, particularly against Taíno women.

Escapees would spread stories of the wild atrocities committed by bearded men who arrived on large boats from across the oceans. Hatuey was a Taíno cacique (chief) on a distant part of the Islands. When  stories of carnage made it to Hatuey, he promptly witnessed the advancing terror to surrounding yucayeques (villages). Hatuey left with about 400 men, women, and children on a fleet of large canoes. He wanted not only to save his people, but to warn others of the impending doom with the hopes of raising an army to stop them. Hatuey would display a basket of gold to other villages and argued:

Here is the God these crazy bearded men worship. They kill us and persecute us because of this metal…and this is why we have to throw it all into the sea. These tyrants tell us they adore a God of peace and tranquility, but yet they take our lands and make us their slaves. They speak to us of an immortal soul and of their eternal rewards, but yet they rob our belongings, rape and violate our women and daughters. These cowards cover themselves in iron that our weapons cannot break.

An artist depiction used in a version of Bartolome de las Casas book illustrating the massacre of Anacaona (a Taína chief) and her people by Columbus’ men.

Some simply didn’t believe Hatuey, since the stories seemed too fanciful. Some did and Hatuey managed to form a small resistance. His army managed to kill a few of Columbus’ men, giving inspiration to those enslaved. This resulted in severe, grotesque retaliation, with Taínos tortured to death for information of Hatuey’s whereabouts. Many months later, Hatuey was caught along with some of his army.

To be made an example of, Hatuey was tied to a stake for a public execution. Before Columbus’ men set fire, a priest explained the concepts of hell and Christianity to save his soul so that he can repent and go to heaven. Hatuey asked the priest, “Will I be in this heaven that you speak of with all of your Christian soldiers?” to which the priest responded “Yes.” Hatuey looked at him with scorn and said, “I would rather go to hell, instead of a place with such cruel people.” Oral histories tell us that Hatuey yelled words of freedom and rebellion against the Columbus’ people before the storming fire deafened his last words.

An illustration used in Bartolome’s book showing Hatuey being burned at the stake.

The combination of diseases (e.g. measles and influenza) introduced by Columbus’ men and genocides, resulted in the extinction of the Taínos – rather, that is what the general public has been led to believe for centuries. The notion of Taíno extinction has been promoted by many American authorities, anthropologists, and other scholars.  This posed massive disadvantages to cultural identities. One only has to glimpse at the long dark history of U.S. treatment towards Native Americans; they essentially destroyed their cultures, justified its actions, then attempt to create an American narrative about their histories – despite that the Natives are still a living culture. There has been an enduring, muzzled fracas among Caribbean cultures and western scholars. Many Caribbean leaders argue their indigenous heritage, that countless Taínos survived the Columbus era and are still alive today. Western scholars stridently say no, hammering into them that the Taínos are wholly extinct.  Anthropologist Maximilian Forte argued at a Cambridge conference that this theme of Taíno extinction in scholarly literature is a motivated narrative for assimilationist discourse,  ideological narrative of western progress of “weaker” people giving up traditions to “stronger” modern ones, symbolic advantages, and for political economic and material advantages. Jorge Estevez, a Taíno and project member at the National Museum of the American Indian, said:

“Paper genocide” practiced by historians ever since, has been just as cruel on my people. With the stroke of their pens, the legacy of my ancestors was wiped out.”

A Mexican stamp commemorating Bartolome de las Casas

The seeds of the Taíno extinction narrative can be traced back to the very people that exploited the Taínos. Spaniard priests that settled in the Caribbeans led a campaign that intentionally over-emphasized the decline of Taíno people to an  80-90% loss due to extreme labor, disease, and physical punishment.  Ironically, this campaign was led by Bartolome de las Casas. This exaggerated narrative was a method for the priests to convince their government to abolish the Encomienda System and to replace it with a missionary system for Taínos. The Encomienda was a bizarre legal economic system that allowed slavery of the Taínos, where their owners had to evangelize and “protect” them in return for their (labor) services,  but that the Taínos had to pay “tribute” to their protectors in the form of gold, foods, and other materials.  The priests believed that by lying about their decline, it would literally save the Taínos. This campaign contributed to changes, particularly the 1512 Leyes de Burgos, which were the first set of laws to cull the ghastly behaviors of its people against the Taínos. It’s 39 laws consisted of stuff such as:

  • For every 50 Taínos, 4 lodges must be built (12-13 Taínos crammed into one 30×15′ unit).
  • Whoever owns 50 Taínos, one boy must be chosen to teach them reading, writing, and Catholicism. This law was more of a brainwashing/assimilation schema: “This boy will then teach the other Indians because the Indians would more readily accept what the boy says than what the Spaniards says…The faith must be ingrained into their heads so the souls of the Indians are saved.”
  • You can no longer physically or verbally abuse Taínos for any reason.
  • Don’t let Taínos sleep on the ground; you must provide hammocks (Although Taínos invented them, they were deprived of hammocks).
  • You must build churches near mines so that Taínos working on Sundays can hear mass.
  • You must feed the Taínos foods (peppers, yams, breads) and one weekly cooked meat meal. If you don’t, you will be fined 2 gold pesos.
  • If you own a Taíno, you must give them 1 gold peso every year (so that they can pay for their own clothing!).

However well-intended Bartolome’s campaign may have been, others began to selfishly capitalize from it, by repeating the (false) significant decline of the Taínos put forth by his campaign. This allowed for many Taíno slave owners to exaggerate their slave losses in order to gain sympathy and persuade their government for permission to import more African slaves  (African slaves were high in demand, because they were stronger and more immune to diseases than Taínos). This doesn’t include the census problem that later trickled into scholarly literature. Many scholars argue that this period kept detailed records, but their censuses generally accounted for Taínos who were kept as slaves in the Encomienda system. It excludes the countless Taínos and imported African slaves who escaped into the depths of Caribbean mountains and forests. This is even documented by military leader Nicolás de Ovando in 1502, writing that Africans escaped with Taínos very often, using the Taínos’ knowledge of the lands to evade slavery. Lynne Guitar, a retired Caribbean anthropologist, argued that these censuses are misleading and unreliable, noting that:

“How can you pretend to count people for a census who are hiding from you?”

Genetic sciences have been catching up, providing the scientific gravitas that has been building a framework of evidence that Taíno ancestry survived to modern day.  The work of a Stanford geneticist was published via Nature that discussed the results of his 1000 Genomes project that sought to reconstruct the genetic variation of indigenous descendants. He found that the people of Puerto Rico has an average of 10-15% Native DNA that is largely Taíno. When discussing the results, Nature added their own thoughts that the Taínos are extinct, but immediately issued a correction:

“This article originally stated that the Taíno were extinct, which is incorrect. Nature apologizes for the offence caused, and has corrected the text to better explain the research project described.”

Nature‘s apologetic-correction has angered some anthropologists and other scholars because they agreed with Nature‘s initial stance, that the Taínos are extinct. Some even argued that the correction show how timorous contemporary scientific culture has evolved. Regardless of the persistent Taíno extinction narrative, other studies keep mounting. Dr. Juan Cruzado,  a Harvard biologist, conducted an island-wide study by testing the DNA of 800 randomly selected islanders and found 61% had mitochondrial DNA of the original indigenous population. A team of 7 biologists conducted a similar study in Cuba, finding a high rate 33% of maternal Native DNA among their sample of 245 unrelated individuals. A team of 21 scientists published the results of a Caribbean-wide genomic study that show indigenous ancestry and its correlation with linguistic and archaeological evidence. While there are many more similar studies, a paramount study by 27 scientists was published in 2018 via Proceedings of the National Academy of Sciences entitled “Origins and Genetic Legacies of the Caribbean Taino.” Their research is based off prehistoric skeletons that were excavated in 2007 from Preacher’s Cave in the Bahamas. They lived some 500 years before Columbus’ journey into the New World and the radiocarbon dated thousand-year-old remains provided the tangible evidence that allowed scientists to implement a relatively new science tool: aDNA, or Ancient DNA.

A Taino mandible excavated from Preacher’s Cave, Bahamas.

Ancient DNA is a method that allows for the extraction of DNA from prehistoric skeletal remains of deceased individuals. From this, scientists can sequence its genome. What all this mean in layman’s terms, is that a person’s DNA can store a ‘book’ full of chapters that tell the historical stories about one’s DNA journey. These stories are written in biological code that our computers can translate. A computer can then take the stories from that one book and compare it to the stories of other books–libraries of other DNAs–informing us of interesting insights, such as migration patterns.  Despite the field of ancient DNA changing our views of the past, there’s a subtle uneasy relationship between archaeology and ancient DNA and a concern for its potential abuse.

One archaeologist, Dr. Phillip Stockhammer quipped:

“Half the archaeologists think ancient DNA can solve everything. The other half think ancient DNA is the devil’s work.”

Stockhammer’s witty remark implies a mild dilemma among some scientists: reluctance to change. Although science is our best tool, its operators are humans. There are many scholars who have built careers on sculpting certain neat narratives that become reinforced by circles in their disciplines. Sadly, their egos will bark when new research or technologies threaten their established territories.  Often, a stranglehold is placed on scientific progress when scholars become gladiators, quarreling that the other is wrong. These stories abound in the history of science, like the stories of Einstein, Alfred Wegener, and Michael Faraday. But that’s another matter, perhaps for a future blog post.  Let’s go back to the 2018 study by 27 scientists. What is most significant about this study, is that it provides the first clear evidence of genetic continuity of Taínos in a modern Caribbean population based on an ancient genome. When comparing the ancient genome to a sample of 104 living Puerto Ricans, they found that 10-15% of their indigenous ancestry are similar to the Taínos than any other indigenous group. The study provides conclusive proof that Taíno indigenous ancestry has survived to modern day. It’s important to note that these findings are unlikely to be exclusive to Puerto Ricans, as future studies will likely reveal Taíno genetic legacies in other Caribbean communities. Dr. Hannes Schroeder, a molecular anthropologist, bioarchaeologist, and lead scientist of the study stated:

“It’s a fascinating finding. Many history books will tell you that the indigenous population of the Caribbean was all but wiped out, but people who self-identify as Taíno have always argued for continuity. Now we know they were right all along: there has been some form of genetic continuity in the Caribbean.”

Elsewhere, Jada Benn Torres, a genetic anthropologist, stated:

“These indigenous communities were written out of history. They are adamant about their continuous existence that they’ve always been on these islands. So to see it reflected in the ancient DNA, it’s great.”

What does all of this intimately mean for the Caribbean peoples, or at least to the people of Puerto Rico? Practically nothing.  While the ancient DNA study might be liberating and uplifting to some, the majority don’t care about what science and other authorities inform them about their culture. Many people on the island have long identified with their Taíno roots, particularly those that live in countrysides and mountainous regions. Generation after generation, the stories of their indigenous ancestors has been orally transmitted, along with the agricultural knowledge and other cultural aspects that are still practiced today. Many of them see the works of science and historians that concerns their histories as a pseudo-sophisticated game where its players have something to argue about, receive trivial awards for constructing false narratives, and collect dishonorable income. My heart sympathizes with them, as Puerto Rico has endured a long, arduous history of oppression at the expense of others. When Spain’s government abolished slavery in 1873, a patchwork of pernicious acts continued in Puerto Rico for the next century, notably those levied by the United States of America. Some examples:

  • The decades-long forced sterilization practices by the U.S that resulted in over 35% of Puerto Rico’s women inability to have children. This was motivated by U.S. eugenics.
  • The U.S. Navy using Vieques as a bombing range for decades, leading to over 20 million pounds of military waste that has leached in the local ecology, desecrating and causing mutations among wildlife, and placing Vieques as the site of the highest rates of cancer and illnesses in Puerto Rico. Clean up efforts still continue to this day.
  • The exploitation of poor, uneducated Puerto Rican women in a large-scale birth control pill trial under misleading information.
  • The United States FBI creating secret files on over 100,000 Puerto Ricans from 1930s to 1990s in an attempt to curb political dissent against the U.S., largely aimed at people who were fighting for independence. These files contained information of a personal nature, from names of sexual partners, copies of personal letters (intercepted at the postal office), to laundry tickets.  These files were not only used politically to deny work and educational opportunities, but to also imprison, fire, and discredit Puerto Ricans. PR was an island of happy, gregarious, and open people, but after 60 years of U.S. spying and informants, it affected the national character of Puerto Rico by etching fear, lying, betrayal, secrecy, and mistrust into its sociological atmosphere. In 2000, the FBI director admitted that “the FBI did operate a program that did tremendous destruction to many people” and to the island of Puerto Rico.
  • A few others include an American doctor injecting cancer cells into Puerto Ricans, radiation experiments, and robber barons who ravaged the native agriculture to turn PR into a cane sugar producing machine for America.

Throughout much of our world history, the cycle of subversion seem to sing the same lyrics: We’ll exploit and destroy everything  now, then we’ll issue a whitewashed-apology in the future. The U.S. Navy has admitted in dumping toxic chemicals like uranium and Agent Orange in Vieques Puerto Rico, but whitewashed that their operations has no correlation to the illnesses that afflict the inhabitants to this day. We’re straying off topic, but hopefully one can understand that the decades of wretchedness cultivated distrust in the hearts of many Puerto Ricans, leading them to loath competing narratives put forth by authorities that attempt to educate them on their own Taíno culture.

The Taínos called Puerto Rico at the time “Borikén,” which means  “The Great Land of the Valiant and Noble Lord” or “Land of the Brave Lords” (referring to their spirits and creator god). “Boricua” is a derivative of Borikén that is a widely use term in modern day to identify others of Puerto Rican culture. The Taínos gave us words that are part of our everyday vocabulary. “Kanowa” eventually carried over to English as “canoe.” “Hurakán” comes from Taíno mythology of the god who created storms, later evolved to English as “hurricane.” “Tabako” becomes “tobacco.” “Hamaka” is now “hammock.” “Wayaba” is “guava” (a tropical fruit). “Barbecue” comes from the Taíno word “Barbakoa.” Other words include iguana, papaya, and manatee.

A modern artist’s painting depicting Tainos and their petroglyphs.

For the majority of the world, the Taínos are long forgotten. They do not receive much press like the Mayans or Incans. The Taínos did not create grand structures or even have a written language. Their ‘language’ was in the form of petroglyphs and art, which can be found in limited books on Taíno art, Caribbean archaeological books and select museums, like the Met Museum in NY.

A 1998 Taino art book by Anthropologist Ricardo Alegria

 

Nowadays, there are statues of Hatuey and of other Taínos around the Caribbeans. Locally, Hatuey is forged as the first freedom fighter of the Americas. The memory of the Taínos are preserved by holding annual Taíno celebrations, local cities and towns maintaining their Taíno names, naming of local structures & organizations (such as an agricultural science research station named in Taíno), and in local products and consumables, like Malta Hatuey.  History is important because it allows one to understand circumstances that create change over time, however admirable or malevolent. Taíno history is important to remember because it’s part of the indigenous ancestry of modern Caribbean cultures and for the rest of the world: a lesson of the horrible, complicit circumstances that contributed to their decline. My grandmother’s ritual of lighting a candle is relatively metaphorical: We keep the history of our ancestors “lit” in our hearts, to ensure that the vile darkness never repeats itself again.

-antonio

A bust of Hatuey “first rebel of America killed by fire in Yara”
A statute of Agüeybaná El Bravo in Puerto Rico, the last known Taino cacique (chief) in Puerto Rico who led the first major conflict (Taino Rebellion of 1511) against colonists with thousands of men.

#Tainos #Boriken

Understanding Evolution: Macroevolution & Major Transitions

Evolution is a fascinating topic that allows you to look at life through the lens of deep time. ‘Deep time’ are vast intervals that cannot be experienced in normal everyday life and it is studied through the science disciplines of geology and paleontology.

But what is ‘evolution’? Is it a fact? Is it a theory?

There are many variants on the definition of evolution, but in the most concise definition, evolution is change over time. More importantly, it is the observable change over time on generations. Changes in a single human individual is not evolution, but developmental. Evolution is concerned with changes on a population.

Evolution is often divided into microevolution and macroevolution. Microevolution refers to change within a species. Species are a group of organisms with shared traits, but a condensed definition of species is a closed gene pool. Macroevolution is when a species changes into another species – a process known as speciation.

Evolution is both a fact and theory.  Across the scientific disciplines, evolution without an argument is a fact. The ‘fact’ stems from the overwhelming amount of evidence of the fossil records, transitional fossils, molecular clock, genetics, and so forth, which also includes facts from laboratory experiments and data from the observable real-world. The ‘theory’ part deals with how we think the fact of evolution has occurred.

In this post, we will be concerned with macroevolutionary transitions.

Macroevolution transitions are that of where some great leap happened, such as a novel mean of adapting to a radical environment. For some examples, think about transitions from sea to the land, the land to the air, the land back to the sea, or salt water to fresh water. Think about leaps in habitats that also forced additional leaps in reproduction.  For example, think of the development on land of both plant seeds and enclosed animal eggs as adaptation to arid environments. Another example is live birth by dolphins, which is an adaptation to marine environments.  Fruits with surrounding seeds that entice hungry animals is an adaptation to enhance plant reproduction.

In turn, some major evolutionary transitions actually changed environments, thus driving additional evolutionary transitions. Think of how the evolution of land plants changed landscapes, the evolution of coral reefs changed seascapes, and evolution flying pollinating insects that changed landscapes.

We can see these sorts of transitions all around us. For example, although modern seals and walruses are adapted to spend most of their lives in marine environments, they are descended from land dwelling animals.  An opposite example are penguins which are in transition from terrestrial to marine environments. They descended from birds that originally flew in the air. They now use their flying ability to great advantage when flying under the water.

Here are some major evolutionary transitions:

  • Eukaryotic cells – the first major transition which happened more than 2 billion years ago.
  • Multi-celled animals – single cell eukaryotes evolved to become multi-celled animals ca. 600-550 ma
  • Skeletons – animals went from softbodied to hardbodied with the development of skeletons and other mineralized parts, whether these evolved with shells, bones or teeth.  Animals with a backbone show up in the fossil record ca. 530 ma.
  • Life on land – This is an interesting transition that happened ca. 500 – 400 ma. Here, plants, fungi, and animals all evolved to live on land that descended from organisms that originally lived in marine environments.
  • Vertebrate origins – Vertebrate also became four-legged and started to walk on land ca. 400 ma.
  • Insect flight and coevolution with seed plants – While vertebrates were beginning to walk on four legs, insects also began to appear ca. 400 – 350 ma. The appearance of insects nearly coincided with the transition of plants with seeds and the first forest.
  • First eggs – The evolution of enclosed animal eggs happened ca. 340 – 310 ma. This was a huge transition. This freed reptiles from watery environments and led to the later evolution of mammals and dinosaurs, as well as flying and swimming reptiles.
  • First flowers – The evolution of flowering plants happened ca. 130 -125 ma. This changed the world as we know it. Not coincidentally, this major transition happened with an evolution of insects into pollinating insects.
  • Mammal origins and evolution – Their evolution originally from reptiles happened ca. 230 ma. Later, they underwent additional evolutionary leaps, such as from egg-laying to giving live birth, and from hoofed land-dwellers to whales.
  • Primate and human origins –  There are several important transitions involved in their overall transitions; from tree dwelling primates to the eventual evolution of humans.

Four Factors that are Responsible for Macroevolutionary Change*

Geographic Isolation

Geographic isolation refers to how populations of a species may become isolated from one another. This include a physical barrier like a mountain chain, a river, or an ocean, that splits a species into different places.  Geographic isolation is not restricted to physical barriers, it simply may be an unfavorable habitat between two populations that prevent them from mating with each other. With enough time, geographic isolation can result in a second factor responsible for macroevolutionary change: genetic drift.

Genetic Drift

This means that a species has drifted enough, genetically speaking, from its ancestral population that it then became a different species or even diversified into many species. We sometimes call this adaptive radiation. It is important to note that while we are speaking of genetic drift in a macroevolutionary sense, genetic drift can also operate on the microevolution level without directly attributing to a new species. Genetic drift on this level concerns itself with fluctuations in allele frequencies on a population due to chance.  One example are the Amish people of Eastern Pennsylvania. They are a closed population that originated from a small number of German immigrants. They inherited rare concentrations of gene mutations from the German founders (hence, the founder effect) that is still active in their population. These mutations causes a number of disorders such as polydactyly (extra fingers) and forms of dwarfism. Because Amish people tend to marry within their population, the recessive genes have a high chance to come together during meiosis which requires two copies of the gene to trigger the disorders.

Environmental Change

Environmental change can be local or global. For example, lowering of sea levels during a time of global cooling would be advantageous for those organisms adapted to cool environment, or to an expansion of land environment.

Mass Extinctions

Mass extinctions are recognized as a factor in macro evolution. There has been 5 mass extinctions (a 6th is currently hypothesized) in the geologic past well before humans showed up. These extinctions occurred 440 ma, 360 ma, 250 ma, 200 ma, and 65 ma. We now suspect that these extinction events while also taking out a lot of species, also led to the opening of habitats and resources for those species that survived. One example is the evolution of dinosaurs from ancestral reptiles that occurred after an extinction event 200ma. Extinctions may have hastened some evolutionary transitions.

These four factors could be summarized by a little phrase coined by Charles Darwin: Natural Selection.  After all, as environments change or mass extinctions take place, organisms in the right place, with the right stuff (genetically speaking), gets selected to pass on those genes to the next generation.  Selection also includes the ‘artificial selection’ that we humans have done through the selective breeding and modification of domestic animals.

*Although we speak of four factors/natural selection that drive macroevolutionary change, it is important to note that there are other roles that attribute to evolutionary changes. We’ll examine a bit of these roles to understand how far science has progressed since Charles Darwin proposed the hypothesis of descent with modification via his 1859  book Origins of Species, which later turned into evolutionary theory.

New science roles that emerged since Darwin’s time include plate tectonics, which helps explain how populations have become geographically isolated in the geologic past.  It also helps to explain how volcanism might have altered the atmosphere, how mountain building and how other earth processes change environments or even influence mass extinctions. Developmental biology  examines how genes code for the development of growing organisms and how these genes might be switched on or off during evolution. Ecology is sophisticated science that looks closely and systematically at how organisms and communities interact with one another and how physical factors in their environments affect and guide their evolution. Modern genetic studies also examine genetic similarity and even help to explain sources of variation. One of the tools that are used in genetic studies include the molecular clock (the general idea  is using calculated rates of change in RNA and DNA to estimate when major transitions may have happened.)

Time-permitting, I will come back to expand on a web series regarding evolution.