Posted: Mar 29, 2011 7:44 pm
The Power of Perspective
The pace of science is astounding. Today we have jumbo jets, iPhones, flat-screen TVs, and myriad other technological doodads hailed as the latest-and-greatest of the modern world, yet people are alive today who lived before man had learned to fly. Who in this not-so-distant past could have foreseen the truly awesome technology of today, and that becomes old news and outdated practically the same year of their release? A century may seem like a long time, and one only speaks of events such as the sinking of the Titanic or man’s first venture of flight as belonging to a bygone era when the world was black and white, and people were just learning to dance. An enlightening jolt it is when one takes in the fact that there are people alive today who witnessed the turn of the 19th century. Could these supercentenarians have ever predicted, even in their most rational reverie, the state of the world in which they would eventually witness in their own biological antiquity? And could they have pondered, in a brief snapshot of their youth, which vein of science would prove to be the most fruitful or important before they take their final bow and the curtains close?
Importance. How does one even begin to address or contextualize the backbone of what is important? The meaning of this term is above all a personal one, and is therefore difficult to pin down without sufficient introspection. One may identify importance on many levels, ranging from the truly personal, to global, and everywhere in between. Another dimension to consider when contemplating importance is time: What is important now versus what will be important in the future? The constraints of the essay topic, however, confine the temporal dimension to that of a single century. And since a century is very roughly one human lifetime, and societal change rarely occurs but over successive generations, what may be societally and globally important may only come to fruition when one considers timescales exceeding that of one-hundred years. How, then, can one care intimately about what is important if they will not live to see the fruits of their labor?
The only solution to this problem is to find something that should be immensely important to the individual, which one can reap the benefits of in their own lifetime, and that will have positive corollaries that pervade on up through society as a whole. A philosophical enlightenment brought about by hard science, then, seems a prime candidate, for nothing (I feel) is more important than an enlightened mind, and the added benefit of an enlightened society, or world, should not need explicit delineation. The scientific field most capable of bringing about this personal and global enlightenment is human population genetics and phylogeography, and more importantly, how it deals with the question of human origins and evolution. Evolution has been called a “universal acid” because of the way it figuratively eating through ones most cherished beliefs and because it seems to permeate through all veins of life and worldly perspective. Human population genetics has the potential to do away with many outdated and dangerous ways of thinking such as racism, sexism, and religion, to name but a few.
Since it is my goal to not only persuade, but to educate, I would like to elucidate and walk through some of the science I feel is of the type needed to enlighten minds and potentially change the world. Our discussion will deal with the science of human origins, and more specifically a comparison of the Out of Africa, and Multiregional hypotheses pertaining to these origins.
Phylogeography, the branch of science that studies the geographic distribution of gene lineages, and therefore the past migratory patterns of species, is grounded on the sturdy foundation of population genetics. The methods of this field have only somewhat recently been applied to our own species, Homo sapiens, and have had some success at settling a debate about human origins that have long plagued the minds of anthropologists and evolutionary biologists alike. What has been known for some time via the fossil record is that Homo erectus, a hominid thought to be a precursor to modern H. sapiens, was extant in Africa about one million years ago (1 Mya), and that what are referred to as “archaic” Homo sapiens (such as H. rhodesiensis, and H. neanderthalensis) came on the scene approximately 300,000 years ago (300 Kya). It was also known that these forms of archaic H. sapiens emerged from Africa and thence became widely distributed throughout Asia and Europe. Now, the question is, did these archaic forms of H. sapiens evolve in situ into modern H. sapiens (Homo sapiens sapiens), or was there another migratory wave that came out of Africa that competitively excluded the archaic forms into extinction? Each hypothesis makes its own set of predictions about what one should find at the genetic level, and those predictions will now be discussed.
The first hypothesis, that archaic forms evolved in situ into modern humans is known as the Multiregional Hypothesis. This model holds that gene flow, though somewhat restricted, is responsible for the spread of modern traits. Furthermore, if modern humans evolved from their respective archaic forms, and their distribution was so vast as to include Africa and Eurasia, then one would expect genetic drift to be significantly limited, which would in turn suggest that substantial genetic differences would have been able to accumulate between populations. The Multiregional Hypothesis predicts that differences found at the genetic level should, in principle, be traceable to differences that evolved between populations of H. erectus, and archaic H. sapiens in Africa, dating back nearly 1 Mya. Also, if I may restate, this model predicts substantial genetic differences between human populations, and also that, since modern man had evolved from archaic forms, modern man should also carry a large subset of archaic DNA. How do the predictions of the Out of Africa Hypothesis (also called the Replacement Hypothesis) differ?
The Out of Africa Hypothesis holds that, while archaic forms spread out of Africa to colonize Eurasia, modern sapiens evolved in Africa, and this modern form then embarked on a second excursion from the motherland into Eurasia, thereby driving archaic sapiens extinct by competitive exclusion without interbreeding. That is, this modern form was a biological species. The predictions of this model are drastically different than that of the Multiregional one in that, for one, we should not expect to find any, or at least very little, Neanderthal DNA in our modern genome. Also, if Africa was the incubator for modern man, we would expect to see the most genetic diversity between African populations, and less and less diversity in populations much farther removed from Africa. The reason for this is that each new population founded away from Africa must have consisted of but a small subset of the population as a whole, in other words, the founding of a new population represents a genetic bottleneck, thereby reducing the genetic variation with every subsequent colonization farther and farther away from Africa.
So, which model is consistent with the facts? In order to make the data more clear, let me first explain a common way one can measure genetic differentiation between populations. Scientists can use a value known as FST, which is equal to the proportion of variance due to differences between populations rather than within populations, which can be depicted mathematically as FST = 1 – (Hw / Hb), where Hw equals the heterozygocity between chromosomes of individuals within the same population, and Hb being equal to the heterozygocity between chromosomes of individuals from different populations. It is not overly important that you firmly grasp this concept mathematically, and it is quite sufficient to know solely that low FST values indicate that differences are found among individuals from the same population rather than in one population but not the other.
Granted, the differentiation in allele frequencies among humans is very low, yet, if the Out of Africa Hypothesis is correct, we should nevertheless expect our values of FST to increase rather smoothly with physical distance between populations. This trend, as predicted, is exactly what we find.
Given the above data, we should then predict, if Africa (more precisely East Africa) was the birthplace of modern H. sapiens, a decrease in genetic diversity as populations are farther and farther removed from Africa. This, too, is exactly what the data indicates.
As you may have guessed, the Out of Africa Hypothesis is currently favored over the Multiregional Hypothesis, and for good reasons. However, there are some data that indicate that some nuclear genes have lineages nearly 2 million years old and seem to have spread not from Africa, but from Asia to the rest of the world including Africa. Odd bit of data indeed, but, despite the few bumps in the road, they do not seem to be deep enough to topple the Out of Africa Hypothesis from its current favored position. The next hundred years, however, will surely illuminate the big picture of Homo sapiens and our phylogeographic patterns.
All of this talk of human origins, genetic diversity, and FST values may all be well and good, but why should anyone care about it? Sure, this kind of knowledge won’t equip you with tools necessary for everyday survival, that is, unless you make a living teaching this sort of stuff, but the value and importance of ideas are not, or at least they should not be, measured solely by whether or not they are conducive to the immediate acquisition of money or material goods. Rather, they should also be measured by the way they enlighten the mind and sow the seeds necessary for further enlightenment. These types of ideas are of tremendous importance above and beyond that of mere gratifying indulgence. Above all, this kind of enlightenment will not be the sort of pseudoenlightenment one gains from religious creeds, since this knowledge is firmly grounded in science.
Pseudoenlightenment, as I have called it, may indeed have benefits to an individual and all those part of the in-group, but ideas—memes—have a tendency to spread like brushfire, and if these ideas are not grounded in evidentiary support, prejudice is bound to run rampant, and society as a whole suffers. In fact, and in large part, racism, homophobia, sexism, and anti-choice movements are the products of a pseudoenlightenment, and the fact that they stem from belief systems based on faith makes them impenetrable to reason. If bad, unfounded ideas can spread so fast (take Mormonism and Scientology for example), shouldn’t well-grounded, good ideas spread all the more quickly? And is there any aspect of society that wouldn’t benefit from a firm grasp of our evolutionary history as a species? Shouldn’t racism wilt with the knowledge that we all originated from a common motherland? And shouldn’t nearly all other aspects of ignorant societal bias equally disintegrate in the wake of a heightened understanding of evolutionary explanations for behavior and a firm grasp of biological processes, unobstructed by the lens of preconceived and miasmic notions of a soul?
Human origin is but a small tile in the mosaic of scientific inquiry, yet each tile is a unique sparkling gem of insight, a tiny aspect of the masterpiece that is reality. If the trend of scientific advance in the past is any indication of what we are to expect in the future, such as the 66 years it took from humankind's first flight in Kitty Hawk to us putting a human on the moon, imagine what the science of phylogeography and population genetics, two areas of research that have only recently taken flight, have in store for us by the end of the century. I feign no guess as to where this branch of science we will be in 100 years time, but I do know that, given the track record of science, our past will be illuminated and we will be in a position of greater enlightenment. Furthermore, if the ideas become viral, the future of humankind will be an environment where faith is no longer a virtue, and understanding reigns supreme.
NOTE: The works cited will be posted as an edit later in the evening. I wanted to make sure the essay itself got up in time. My apologies.
WORKS CITED:
Avise, J. 2000. Phylogeography. Harvard UP, Cambridge, MA. [6]
Coop, Graham. 2011. Introduction to evolution (EVE 100). University of California, Davis. Winter quarter PowerPoint lecture.
Finlayson, C. 2005. Biogeography and evolution of the genus Homo. Trends Ecol. Evol. 20:457-463. [6]
Futuyma, Douglas. 1998. Evolutionary Biology 3rd Edition. Sunderland , MA: Sinauer Associates Inc.
---, Evolution. 2009. Sunderland , MA: Sinauer Associates Inc.
Garrigan, D., and M. F. Hammer. 2006. Reconstructing human origins in the genomic era. Nature Rev. Genet. 7:669-680. [6]
Green, R E., et al. 2006. Analysis of one million base pairs of Neanderthal DNA. Nature 444:330-336. [6, 20]
Horai, s., et al. 1995. Recent African origin of humans revealed by complete sequences of hominid mitochondrial DMAs. Proc. Natl. Acad. Sci. USA 92:532-536. [26]
Ruvolo, M., et al. 1993. Mitochondrial COII sequences and modern human origins. Mol. Biol. Evol. 10:1115-1135. [26]
Takahata, N. 1995. A genetic perspective on the origin and history of humans. Annu. Rev. Ecol. Syst. 26:343-372. [26]
Templeton, A. R. 2007. Genetics and recent human evolution. Evolution 61: 1507-1519. [6]
Vigilant, L et al. 1991. African populations and the evolution of human mitochondrial DNA. Science 253: 1503-1507. [26]
Wolpoff, N. 1989. Multiregional Evolution: The fossil alternativeto Eden. In P. Mellars and C. Stringer (eds), The Human Revolution, pp. 62-108. Princeton UP, Princeton, NJ.
The pace of science is astounding. Today we have jumbo jets, iPhones, flat-screen TVs, and myriad other technological doodads hailed as the latest-and-greatest of the modern world, yet people are alive today who lived before man had learned to fly. Who in this not-so-distant past could have foreseen the truly awesome technology of today, and that becomes old news and outdated practically the same year of their release? A century may seem like a long time, and one only speaks of events such as the sinking of the Titanic or man’s first venture of flight as belonging to a bygone era when the world was black and white, and people were just learning to dance. An enlightening jolt it is when one takes in the fact that there are people alive today who witnessed the turn of the 19th century. Could these supercentenarians have ever predicted, even in their most rational reverie, the state of the world in which they would eventually witness in their own biological antiquity? And could they have pondered, in a brief snapshot of their youth, which vein of science would prove to be the most fruitful or important before they take their final bow and the curtains close?
Importance. How does one even begin to address or contextualize the backbone of what is important? The meaning of this term is above all a personal one, and is therefore difficult to pin down without sufficient introspection. One may identify importance on many levels, ranging from the truly personal, to global, and everywhere in between. Another dimension to consider when contemplating importance is time: What is important now versus what will be important in the future? The constraints of the essay topic, however, confine the temporal dimension to that of a single century. And since a century is very roughly one human lifetime, and societal change rarely occurs but over successive generations, what may be societally and globally important may only come to fruition when one considers timescales exceeding that of one-hundred years. How, then, can one care intimately about what is important if they will not live to see the fruits of their labor?
The only solution to this problem is to find something that should be immensely important to the individual, which one can reap the benefits of in their own lifetime, and that will have positive corollaries that pervade on up through society as a whole. A philosophical enlightenment brought about by hard science, then, seems a prime candidate, for nothing (I feel) is more important than an enlightened mind, and the added benefit of an enlightened society, or world, should not need explicit delineation. The scientific field most capable of bringing about this personal and global enlightenment is human population genetics and phylogeography, and more importantly, how it deals with the question of human origins and evolution. Evolution has been called a “universal acid” because of the way it figuratively eating through ones most cherished beliefs and because it seems to permeate through all veins of life and worldly perspective. Human population genetics has the potential to do away with many outdated and dangerous ways of thinking such as racism, sexism, and religion, to name but a few.
Since it is my goal to not only persuade, but to educate, I would like to elucidate and walk through some of the science I feel is of the type needed to enlighten minds and potentially change the world. Our discussion will deal with the science of human origins, and more specifically a comparison of the Out of Africa, and Multiregional hypotheses pertaining to these origins.
Phylogeography, the branch of science that studies the geographic distribution of gene lineages, and therefore the past migratory patterns of species, is grounded on the sturdy foundation of population genetics. The methods of this field have only somewhat recently been applied to our own species, Homo sapiens, and have had some success at settling a debate about human origins that have long plagued the minds of anthropologists and evolutionary biologists alike. What has been known for some time via the fossil record is that Homo erectus, a hominid thought to be a precursor to modern H. sapiens, was extant in Africa about one million years ago (1 Mya), and that what are referred to as “archaic” Homo sapiens (such as H. rhodesiensis, and H. neanderthalensis) came on the scene approximately 300,000 years ago (300 Kya). It was also known that these forms of archaic H. sapiens emerged from Africa and thence became widely distributed throughout Asia and Europe. Now, the question is, did these archaic forms of H. sapiens evolve in situ into modern H. sapiens (Homo sapiens sapiens), or was there another migratory wave that came out of Africa that competitively excluded the archaic forms into extinction? Each hypothesis makes its own set of predictions about what one should find at the genetic level, and those predictions will now be discussed.
The first hypothesis, that archaic forms evolved in situ into modern humans is known as the Multiregional Hypothesis. This model holds that gene flow, though somewhat restricted, is responsible for the spread of modern traits. Furthermore, if modern humans evolved from their respective archaic forms, and their distribution was so vast as to include Africa and Eurasia, then one would expect genetic drift to be significantly limited, which would in turn suggest that substantial genetic differences would have been able to accumulate between populations. The Multiregional Hypothesis predicts that differences found at the genetic level should, in principle, be traceable to differences that evolved between populations of H. erectus, and archaic H. sapiens in Africa, dating back nearly 1 Mya. Also, if I may restate, this model predicts substantial genetic differences between human populations, and also that, since modern man had evolved from archaic forms, modern man should also carry a large subset of archaic DNA. How do the predictions of the Out of Africa Hypothesis (also called the Replacement Hypothesis) differ?
The Out of Africa Hypothesis holds that, while archaic forms spread out of Africa to colonize Eurasia, modern sapiens evolved in Africa, and this modern form then embarked on a second excursion from the motherland into Eurasia, thereby driving archaic sapiens extinct by competitive exclusion without interbreeding. That is, this modern form was a biological species. The predictions of this model are drastically different than that of the Multiregional one in that, for one, we should not expect to find any, or at least very little, Neanderthal DNA in our modern genome. Also, if Africa was the incubator for modern man, we would expect to see the most genetic diversity between African populations, and less and less diversity in populations much farther removed from Africa. The reason for this is that each new population founded away from Africa must have consisted of but a small subset of the population as a whole, in other words, the founding of a new population represents a genetic bottleneck, thereby reducing the genetic variation with every subsequent colonization farther and farther away from Africa.
So, which model is consistent with the facts? In order to make the data more clear, let me first explain a common way one can measure genetic differentiation between populations. Scientists can use a value known as FST, which is equal to the proportion of variance due to differences between populations rather than within populations, which can be depicted mathematically as FST = 1 – (Hw / Hb), where Hw equals the heterozygocity between chromosomes of individuals within the same population, and Hb being equal to the heterozygocity between chromosomes of individuals from different populations. It is not overly important that you firmly grasp this concept mathematically, and it is quite sufficient to know solely that low FST values indicate that differences are found among individuals from the same population rather than in one population but not the other.
Granted, the differentiation in allele frequencies among humans is very low, yet, if the Out of Africa Hypothesis is correct, we should nevertheless expect our values of FST to increase rather smoothly with physical distance between populations. This trend, as predicted, is exactly what we find.
Given the above data, we should then predict, if Africa (more precisely East Africa) was the birthplace of modern H. sapiens, a decrease in genetic diversity as populations are farther and farther removed from Africa. This, too, is exactly what the data indicates.
As you may have guessed, the Out of Africa Hypothesis is currently favored over the Multiregional Hypothesis, and for good reasons. However, there are some data that indicate that some nuclear genes have lineages nearly 2 million years old and seem to have spread not from Africa, but from Asia to the rest of the world including Africa. Odd bit of data indeed, but, despite the few bumps in the road, they do not seem to be deep enough to topple the Out of Africa Hypothesis from its current favored position. The next hundred years, however, will surely illuminate the big picture of Homo sapiens and our phylogeographic patterns.
All of this talk of human origins, genetic diversity, and FST values may all be well and good, but why should anyone care about it? Sure, this kind of knowledge won’t equip you with tools necessary for everyday survival, that is, unless you make a living teaching this sort of stuff, but the value and importance of ideas are not, or at least they should not be, measured solely by whether or not they are conducive to the immediate acquisition of money or material goods. Rather, they should also be measured by the way they enlighten the mind and sow the seeds necessary for further enlightenment. These types of ideas are of tremendous importance above and beyond that of mere gratifying indulgence. Above all, this kind of enlightenment will not be the sort of pseudoenlightenment one gains from religious creeds, since this knowledge is firmly grounded in science.
Pseudoenlightenment, as I have called it, may indeed have benefits to an individual and all those part of the in-group, but ideas—memes—have a tendency to spread like brushfire, and if these ideas are not grounded in evidentiary support, prejudice is bound to run rampant, and society as a whole suffers. In fact, and in large part, racism, homophobia, sexism, and anti-choice movements are the products of a pseudoenlightenment, and the fact that they stem from belief systems based on faith makes them impenetrable to reason. If bad, unfounded ideas can spread so fast (take Mormonism and Scientology for example), shouldn’t well-grounded, good ideas spread all the more quickly? And is there any aspect of society that wouldn’t benefit from a firm grasp of our evolutionary history as a species? Shouldn’t racism wilt with the knowledge that we all originated from a common motherland? And shouldn’t nearly all other aspects of ignorant societal bias equally disintegrate in the wake of a heightened understanding of evolutionary explanations for behavior and a firm grasp of biological processes, unobstructed by the lens of preconceived and miasmic notions of a soul?
Human origin is but a small tile in the mosaic of scientific inquiry, yet each tile is a unique sparkling gem of insight, a tiny aspect of the masterpiece that is reality. If the trend of scientific advance in the past is any indication of what we are to expect in the future, such as the 66 years it took from humankind's first flight in Kitty Hawk to us putting a human on the moon, imagine what the science of phylogeography and population genetics, two areas of research that have only recently taken flight, have in store for us by the end of the century. I feign no guess as to where this branch of science we will be in 100 years time, but I do know that, given the track record of science, our past will be illuminated and we will be in a position of greater enlightenment. Furthermore, if the ideas become viral, the future of humankind will be an environment where faith is no longer a virtue, and understanding reigns supreme.
NOTE: The works cited will be posted as an edit later in the evening. I wanted to make sure the essay itself got up in time. My apologies.
WORKS CITED:
Avise, J. 2000. Phylogeography. Harvard UP, Cambridge, MA. [6]
Coop, Graham. 2011. Introduction to evolution (EVE 100). University of California, Davis. Winter quarter PowerPoint lecture.
Finlayson, C. 2005. Biogeography and evolution of the genus Homo. Trends Ecol. Evol. 20:457-463. [6]
Futuyma, Douglas. 1998. Evolutionary Biology 3rd Edition. Sunderland , MA: Sinauer Associates Inc.
---, Evolution. 2009. Sunderland , MA: Sinauer Associates Inc.
Garrigan, D., and M. F. Hammer. 2006. Reconstructing human origins in the genomic era. Nature Rev. Genet. 7:669-680. [6]
Green, R E., et al. 2006. Analysis of one million base pairs of Neanderthal DNA. Nature 444:330-336. [6, 20]
Horai, s., et al. 1995. Recent African origin of humans revealed by complete sequences of hominid mitochondrial DMAs. Proc. Natl. Acad. Sci. USA 92:532-536. [26]
Ruvolo, M., et al. 1993. Mitochondrial COII sequences and modern human origins. Mol. Biol. Evol. 10:1115-1135. [26]
Takahata, N. 1995. A genetic perspective on the origin and history of humans. Annu. Rev. Ecol. Syst. 26:343-372. [26]
Templeton, A. R. 2007. Genetics and recent human evolution. Evolution 61: 1507-1519. [6]
Vigilant, L et al. 1991. African populations and the evolution of human mitochondrial DNA. Science 253: 1503-1507. [26]
Wolpoff, N. 1989. Multiregional Evolution: The fossil alternativeto Eden. In P. Mellars and C. Stringer (eds), The Human Revolution, pp. 62-108. Princeton UP, Princeton, NJ.