The odd response to global warming warnings

The recent release of the latest IPCC report on global warming gives a comprehensive review of the current state of knowledge and represent an overwhelming scientific consensus on the nature of the problem confronting us.

The report’s conclusions paint a gloomy picture:

The report states in unequivocal terms that the climate is warming globally and that since the middle of the 20th century, human industrial activity – the burning of fossil fuels and, to a lesser extent, land-use changes – is warming’s main driver. Since the last report in 2001, confidence in that statement has risen from “likely” (greater than a 66 percent chance) to “very likely” (greater than 90 percent).

• Temperatures are “likely” to rise 2 degrees to 4.5 degrees Celsius by the end of the century, if CO2 concentrations reach twice their preindustrial level. Within that range, the most likely result is 3 degrees C (5.4 degrees Fahrenheit). That additional warmth will distribute itself unevenly, with the highest increases in the Arctic and progressively smaller increases farther south.

• Sea levels could rise by century’s end from 28 to 58 centimeters (11 to 23 inches) above 1999 levels globally. That’s a narrower range than the IPCC offered in 2001, when it projected a range of 9 to 88 centimeters. Even if CO2 concentrations could be stabilized at twice preindustrial levels by 2100, thermal expansion of the oceans alone could raise sea levels an additional 1 to 3 feet by 2300. But recent research also suggests that the Greenland ice sheet is losing mass faster than expected, leaving open the possibility that sea-level increases will be higher if the melting trend continues to accelerate. If Greenland’s ice cap continues to lose mass over the next 1,000 years, the entire ice cap would vanish, raising sea levels by some 23 feet.

What is interesting is the response of the global warming deniers. The Guardian newspaper reports that the so-called ‘think tank’ the American Enterprise Institute is actually trying to bribe scientists to dispute the report. Funded with $1.6 million from Exxon-Mobil, the AEI is offering scientists $10,000 each “for articles that emphasise the shortcomings of a report from the UN’s Intergovernmental Panel on Climate Change (IPCC).” They are also willing to pay for travel and other perks. (Stephen Colbert comments on the bribes.)

Ben Stewart of Greenpeace is quoted as saying: “The AEI is more than just a thinktank, it functions as the Bush administration’s intellectual Cosa Nostra. They are White House surrogates in the last throes of their campaign of climate change denial. They lost on the science; they lost on the moral case for action. All they’ve got left is a suitcase full of cash.”

That sounds like an accurate description to me.

The Guardian report also says that an Exxon-funded organization in Canada will launch a review that will challenge the IPCC report. One of the people involved is Nigel Bellamy. Some of you may recall an earlier posting of mine that discussed how his sloppy work was exposed by George Monbiot.

There is one thing about the global warming debate that puzzled me and that is the vehemence of the opposition by some ordinary people to the idea. I can understand why the big emissions-producing industries and their allies in the Bush administration are fighting the idea that global warming is occurring. They do not want to take any action that might cut into their profits.

But why are some ordinary people so emphatically opposed to this finding of the scientific community? It is not like evolution or stem-cell research where science is treading on religious toes. As far as I can tell, there are no Biblical issues here, no eleventh commandment to the flock to, yeah verily, go out and emit CO2 in abundance until the glaciers melteth into the seas.

I am not talking about people who are simply skeptical about the scientific case being made that global warming is a real threat and that it is largely caused by human activity. That kind of skepticism is understandable but does not usually create the level of passion that is characteristic of the global warming deniers.

On global warming you find what seems to be ordinary people going out of their way to ridicule the emerging scientific consensus. This is surprising because most ordinary people do not go to great lengths to ridicule those areas in which there is scientific consensus. You do not find passionate opposition to, say, scientific community suggestions on reducing transfats or warning about the dangers of smoking.

It is almost as if the members of the public who are skeptics think that the scientific community is trying to pull a fast one on them. But why would they think this? There is no advantage to scientists in global warming. Scientists get no benefit from warning about the danger. At most they can be accused of being over-cautious.

So why this unusual level of hostility to the idea that global warming might be real? Is this coming from people who are angry with scientists about other things that do offend their religious sensibilities and are now out to attack anything that scientists say that might affect their lives? Or are these people part of an “astroturf” (i.e. fake grass roots) movement funded by the oil industry and polluting companies? Or are these people who, for ideological reasons, will side with Bush and big corporations come what may, whatever the issue? Or is there some other reason that I am missing?

These are not rhetorical questions. I am genuinely puzzled as to why this is so. Any suggestions?

POST SCRIPT: Talk by Israeli academic and peace activist

Jeff Halper, an emeritus professor of anthropology at Ben Gurion University and an Israeli peace activist, will be talking today at Case. The talk is free and open to the public.

When: 4:30pm, Monday, February 19, 2007
Where: Clark 309

I have written before about Professor Halper’s last visit to Case in May 2005 and how his talk was a revelation to me about what was happening in the occupied territories.

The flyer for his visit this time says:

Dr. Jeff Halper, the Coordinating Director of the Israeli Committee Against House Demolitions was a 2006 nominee for the Nobel Peace Prize. He is an Israeli-American peace activist, professor of anthropology, distinguished author and internationally acclaimed speaker. The 3rd edition of his popular book, “Obstacles to Peace: A Reframing of the Palestinian-Israeli Conflict” was released in 2005. Halper has forged a new mode of Israeli peace activity based on nonviolent direct action and civil disobedience to the Israeli Occupation. Through its resistance to the demolition of Palestinian homes and other manifestations of the Occupation, including the rebuilding of demolished homes as acts of political solidarity, ICAHD has developed a relationship of trust and close cooperation with Palestinian organizations. Believing that civil society and governmental forces must be mobilized if a just peace is to emerge in Israel/Palestine, Jeff also directs ICAHD’s extensive program of international advocacy. His popular book Obstacles to Peace is to be followed by a forthcoming work: An Israeli in Palestine: Reframing the Israel-Palestine Conflict (Pluto Press).

The joy of free thinking

(Due to the holidays, I will be taking a break from blogging. New posts will begin on Wednesday, January 3, 2007.)

There is scarcely a week that does not pass without some interesting new scientific discovery about the nature of life. You open the newspaper and read of observations of light emitted by distant stars from the very edges of the known universe, light that must have been emitted almost at the very beginning, over ten billion years ago. Such research puts us in touch with our own cosmic beginnings. See this video for images from the Hubble Space telescope of the deep field that shows galaxies nearly 80 billion light years away. It is at once humbling to realize that we are but a speck in the vast regions of space who occupy a flicker of time, while also exhilarating that despite these limitations of space and time, we have been able, thanks to science, to learn so much about the universe we live in.

Just recently there was the discovery of the fossils a possible new Hobbit-like people who lived in a remote island in the Indonesian archipelago about 18,000 years ago. Then there was the discovery in China of an almost perfectly preserved bowl of noodles that is about the 4,000 years old. Discoveries like these shed light on how evolution works and how human society evolved.

Similarly, the discoveries that come from studies of DNA tell us a lot about where humans probably originated, how we are all related to one another and how, despite our common origins, the species spread over the Earth and diversified. The fact (according to the September 21, 2005 issue of The Washington Post) that we share over 90 percent of our DNA with chimpanzees, lend further strong support (not that it needed it) to the evolutionary idea that chimpanzees and humans share a common ancestry.

I enjoy reading things like this because it reminds me that we are all linked together by one great biological evolutionary tree, with the various animal species being our cousins, and even things like worms and bacteria being somehow related to us, however distantly. Some people may find the idea of being related to a monkey repulsive but I think it is fascinating. The ability of science to investigate, to find new relationships, to explore and conjecture and come up with answers to old questions as well as create new questions to investigate is one of its greatest qualities.

And for me, personally, being an atheist makes that joy completely unalloyed. Shafars (i.e., secularists, humanists, atheists, freethinkers, agnostics, and rationalists), as well as religious people who interpret their religious texts metaphorically and not literally, do not have any concerns when new headlines describing a new scientific discovery are reported in the news. They do not have to worry whether any new fact will contradict a deeply held religious belief. They do not have to worry about whether they need to reconcile the new information with any unchanging religious text.

On the other hand, the same news items that give us fascinating glimpses of scientific discoveries undoubtedly create fresh headaches for those whose religious beliefs are based on literal readings of religious texts, because each new discovery has to be explained away if it disagrees with some dogma. There are people who devote their entire lives to this kind of apologetics, to ensure that their religious beliefs are made compatible with science. The website Answers in Genesis, for example, is devoted to making Young-Earth creationism (YEC) credible. So it goes to great lengths to show that the earth is less that 10,000 years old, all the animals could have fitted into Noah’s Ark, and that dinosaurs lived at the same time as humans.

One has to admire the tenacity of such people, their willingness to devote enormous amounts of time, sometimes their whole lives, to find support for a belief structure that is continuously under siege from new scientific discoveries. It must feel like trying to hold back the tide. (See this site which tries to fit the astrophysical data received from light emitted by stars that are billions of light years away into a 10,00 year old universe model.)

Of course, scientific discoveries come too thick and fast for even the most determined literal apologists to keep up. So they tend to focus only on explaining away a few questions, the kinds of questions that the lay public is likely to be concerned about, such as whether dinosaurs existed concurrently with humans, the ages of the universe and the Earth, whether the size of the Ark was sufficient to accommodate all the species, how Noah coped with the logistical problems of feeding all the animals and disposing of the waste, how Adam and Eve’s children could multiply without there already being other people around or indulging in incest, and so on.

But the rest of us don’t have to worry about any of that stuff and so can enjoy new scientific discoveries without any cares, and follow them wherever they lead. It is nice to know that one can throw wide open the windows of knowledge and let anything blow in, clearing out the cobwebs of old ideas and freshening up the recesses of the mind.

It is a wonderful and exhilarating feeling.

Can the curriculum at Hogwarts be called science?

(Due to the holidays, I will be taking a break from blogging. Instead, I will be re-posting some of my more light-hearted essays, this week dealing with the Harry Potter books. New posts will begin on Wednesday, January 3, 2007.

I have somehow completed another full year of blogging. Over the year I have made about 250 posts, written over three hundred thousand words, and had a total of about 750,000 hits. In the process of researching for the posts, I have learned a lot.

I would like to thank all the people who visited, read, and commented. It has been a real pleasure and I wish all of you the very best for 2007.)

Science fiction writer Arthur C. Clarke makes the point that any sufficiently advanced technology will seem like magic to the naïve observer. This seems to be a good observation to apply to the magic that is practiced at Hogwarts. What seems to exist there is a world with highly advanced “technology”, operating under strict rules that the inhabitants know how to manipulate. The more mature wizards seem to easily produce consistent results with their spells while the novices mess around until they get it right. This is not very different from what we do in the Muggle world, except that we are manipulating computers and cars that are controlled by knobs and dials and switches and keyboards, while the wizards use wands and spells. It is not a mystery to other wizards how specific results are obtained and what is required to achieve those results is skill and practice.
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The problem with parallel worlds

(Due to the holidays, I will be taking a break from blogging. Instead, I will be re-posting some of my more light-hearted essays, this week dealing with the Harry Potter books. New posts will begin on Wednesday, January 3, 2007.)

Fantasy writers like J. K. Rowling who want to interweave the magical with the ordinary face some serious challenges. As long as you stay purely within the world of magic at Hogwarts, you can create a self-contained world obeying its own rules. But there is clearly some added drama that accrues when you can contrast that world with the world we live in, because that helps readers to identify more with the characters. Having wizards live among Muggles opens up plenty of opportunities for both comedy and dramatic situations. It also enables us to imagine ourselves in the story, to think that there might be a parallel world that we get glimpses of but do not recognize because we do not know what to look for. Maybe our neighbors are witches and we don’t know it.

The situation faced by authors like Rowling in coming up with a realistic scenario that convincingly weaves the magic and ordinary worlds is not unlike the problem facing religious people who believe in a parallel world occupied by god, heaven, angels, etc. For this parallel religious world to have any tangible consequences for people in the normal world, the two worlds must overlap at least at a few points. But how can you make the intersections consistent? How can god, who presumably exists in the parallel universe, intervene in the natural world and yet remain undetected? In a previous posting, I discussed the difficult questions that need to be addressed in making these connections fit into a coherent worldview.

In Rowling’s world, one connecting point between the magical and normal worlds is the pub The Leaky Cauldron whose front door opens onto the normal world and whose back has a gate that opens onto Diagon Alley, a parallel magical world. Another connecting point is at Kings Cross railway station where the brick wall between platforms nine and ten is a secret doorway onto platform 9 ¾, where the students catch the train to Hogwarts. A third is the house at 12 Grimmauld Place, and so on.

But this plot device of having gateways connecting the two worlds, while amusing, creates problems if you try to analyze it too closely. (This is the curse of many, many years of scientific training, coupled with a determinedly rationalistic worldview. It makes me want to closely analyze everything, even fiction, for internal logical consistency.)

For example, although platform 9 ¾ is hidden from the Muggles in some kind of parallel world, the train to Hogwarts somehow seems to get back into the real world on its way to Hogwarts because it travels through the English countryside. I initially thought that this countryside might also be in the parallel world, except that in one book Ron and Harry catch up with the train in their flying car, and they started off in the normal world. In another book we are told that Hogwarts is also in the Muggle world but that it is charmed so that Muggles only see what looks like a ruined castle. We also see owls carrying mail between Hogwarts and the normal world. So clearly there must be many boundaries between the magic and Muggle worlds. What happens when people and owls cross these other boundaries?

When I read the books, such questions are for me just idle curiosity. I like to see how the author deals with these questions but the lack of logical consistency does not really bother me or take anything away from my enjoyment of the books. Rowling is not sloppy. She respects her readers’ intelligence, and she gives the reader enough of a rationale for believing in her two-worlds model that we can be taken along for the ride. The logical inconsistencies she glosses over are, I think, unavoidable consequences of trying to create this kind of parallel universe model, not unlike those encountered by science fiction writers striving for plausibility. To her credit, she is skilful enough to provide enough plausibility so that the reader is not troubled (or even notices) unless he or she (like me) is actually looking for problems.

But the problems Rowling faces in constructing a two worlds model that is logically consistent is similar to that faced by people who want to believe in a spiritual world that exists in parallel with the physical world. Since Rowling is writing a work of fiction and nothing of importance rides on whether we accept the inconsistencies or not, we can just close our eyes to these minor flaws and enjoy the books.

But the same cannot be said for the similar problems that confront two-world models that underlies most religious beliefs that have a god, because we are now not dealing with fiction but presumably real life. And being able to construct a two-worlds model (with gateways between the spiritual and physical worlds) that is logically consistent is important because it may determine whether people believe or disbelieve in a god.

It was my personal inability to be able to do this that finally convinced me to become an atheist.

POST SCRIPT: Going to church

Homer Simpson makes the case for not doing so.

Emotional reactions to Darwin

There is no doubt that Darwin’s ideas about evolution by natural selection carry a huge emotional impact. For many people the idea that “we are descended from apes” is too awful to contemplate and is sufficient reason alone to dismiss any claim that natural selection holds the key to understanding how we came about. (Of course, we are not descended from apes. The more accurate statement is that apes and humans share common ancestors, making them our cousins, but even this refinement does not take away the stigma that supposedly comes with being biologically related to animals such people consider inferior.)

This unease about being biologically linked to other species is widespread and transcends any particular religious tradition. In Sri Lankan rural areas, one would frequently see monkeys on trees by the side of the road. As children when we were passing them, almost invariably someone would point them out and say things like “Your relatives have come to see you.” Similarly, if one said that one was going to visit the zoo, this would also result in the question as to whether one was going to visit one’s relatives. This kind of humor among children was commonplace, and reflected a reflexive instinct that humans were superior to all other animal forms, and reinforced the belief that some sort of special creative process must have been at work to produce us.
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Looking for deep ancestors

Richard Dawkins in his book The Ancestor’s Tale (2004) tells a fascinating story. He models his book on a journey that, rather than moving through space to a particular destination, is moving in the temporal dimension, going steadily back in time. He calls it a “pilgrimage to the dawn of evolution.” He starts with present day humans and follows them back into history. One reason he gives for going back in time instead of starting at the beginning and going forwards as is more commonly done is to avoid a common trap of perception. When you tell the story forwards, it is hard to avoid giving the impression that life evolved purposefully, that human beings were somehow destined to be. This is counter to evolutionary theory that says that evolution is not directed towards any goal. It tells us how the present emerged from the past. It does not tell us how the future will emerge from the present.

Dawkins points out that the another advantage of telling the story backwards is that you can choose any of the current species and go back in time and tell pretty much the same story.

As I have mentioned earlier, we quickly (in just 2,000 years) reach the time when the most recent common ancestor lived and soon after that (about 5,000 years ago) reach a point when all our ancestors were identical.

But this convergence of ancestry is not just for humans, it is for all species. If we go far enough back in time, even my dog Baxter and I share the same ancestor, which I find a very appealing notion.

Anyway, here is a concise summary of the landmarks on this pilgrimage back in time, along with some other landamrks.

About 10,000 years ago, the agricultural revolution began and about 12,000 years ago saw the beginnings of language. About 160,000 years ago saw the beginning of what we would consider modern humans, and beyond that we start reaching the precursors to modern humans, a famous milestone being the fossil Lucy, dated to 3.2 Mya (million years ago).

As we go further back in time in this pilgrimage, other species start ‘joining us’ in our journey. What this means is that we reach times at which an earlier species existed which then split into two branches and diverged evolutionarily to what we see now. So if we go back further in time, we should cease to view the pilgrims on the journey as a combined group of humans and other species but instead see the travelers as that earlier common ancestor species. He calls these common ancestors ‘concestors’. (Concestor 0 in Dawkins’ scheme is the most recent common ancestor of all humans (or MRCA) that I have discussed earlier and who lived just a few thousand years ago.)

Going back in time, at 6 Mya we meet concestor 1 when we join up with the ancestors of chimpanzees. As we go even back further, we (and when I say ‘we’, I remind you that we should not think of ‘us’ as humans at this point but as the common ancestor species of humans and chimpanzees) join up at about 40 Mya successively with gorillas, orang utans, gibbons, and finally monkeys. Remember that the ‘pilgrims’ look different as we pass each concestor point.

Concestor 8 occurs at about 63 Mya when we join up with mammals like lemurs and lorises. (Just prior to this, around 65 Mya, was when all the dinosaurs went extinct.) As you can imagine, concestor 8 would not look much like present-day humans at all.

About 75 Mya, we join up with rats, rabbits and other rodents (concestor 10), at 85 Mya with cats and dogs (concestor 11), at 105 Mya with elephants and manatees (concestor 13), at 310 Mya with snakes and chickens (concestor 16).

At 340 Mya, we make a big transition when join up with the ancestors of amphibians, such as frogs and salamanders (concestor 17). This point marks the first time that animals moved out of the water.

Around 440 Mya we join up with various kinds of fish (concestor 20), and around 630 Mya with flatworms (concestor 27).

After various other species ancestors’ join ours, the next big rendezvous occurs at about 1,100 Mya when we join up with the ancestors of fungi, such bread molds and truffles (concestor 34).

Some time earlier than that (passing the connection with amoeba at concestor 35) but before 1,300 Mya (it is hard to pin the date) is when the next major transition occurs when we join up with green plants and algae. This common ancestor is concestor 36.

At about 2,000 Mya we arrive at concestor 38 where every species is now represented by a eukaryotic (nucleated) cell.

At about 3,500 Mya we meet up with our earliest ancestors, the eubacteria (concestor 39), the original form of life.

Dawkins’ reverse story can be seen visually, told in a beer commercial in 50 seconds flat to the pounding beat of Sammy Davis Jr. singing The Rhythm of Life. (A minor quibble: There is one way in which this fun visual representation is not accurate. It shows three humans going back in evolution until we join up with ancestors of the present-day amphibians (concestor 17) in identical parallel paths. This is ruled out by the reductio ad absurdum argument written about earlier, where it was established that all present day humans must have had a single common ancestor in any earlier species.)

I must say that this book was an exhilarating journey. To see the whole of the evolution of life going backwards and merging together was a nice new way of seeing the process. Those of you who are interested in the grand sweep of evolution written for a non-specialist will find Dawkins’ book a great resource.

POST SCRIPT: The Boxer

A live performance of Simon and Garfunkel singing one of my all-time favorite songs The Boxer

My ancestor Pharaoh Narmes again

I began this series of posts saying that I had discovered that there was an 80% chance that I was descended from Narmes, the first pharaoh of a united Egypt. As subsequent posts have indicated, I arrived at this, not by any detailed investigative work in tracking my lineage, but by depending upon the analysis of Douglas L. T. Rohde, Steve Olson, and Joseph T. Chang and published in the journal Nature.

After reading that paper, I became curious about who lived around the time of the identical ancestors and looked around to see if there was a named individual. I knew that writing was discovered around 5,000 years ago, so the time of the IA (identical ancestors) coincided roughly with the time that written records were starting to be kept. So there was a chance that there was a reliable contemporaneous written record of some person from the time of the IA. The chances were also great that the person whose life was recorded was likely to have been a big shot, a king or some such, whom people considered important enough to write about, on tombs and so forth.
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Sexual selection

In a previous post, I discussed the fact that although all of us have the identical set of ancestors who lived just 5,000 years ago, this does not mean that we have the same genes. The fact that we are different is due to the fact that if most of the mating occurs within a group, then this can result in certain features becoming emphasized. In extreme case, this initial isolated mating pattern can result in a new species being formed that cannot mate with other groups that it could have done in the past.

I had always thought that the two organisms belonged to different species if they were biologically different enough that they either could not produce offspring or, as in the case of mules produced by horses and donkeys, the offspring were infertile and thus not able to reproduce.

But I learned from Richard Dawkins’ book The Ancestor’s Tale (2004) that two things can be considered different species even if they are perfectly capable of producing fertile offspring. All that is required for them to be considered to be different species is that they are not found to mate in the wild for whatever reason.

Normally, this happens when there is some kind of barrier that separates two groups of the same species so that they cannot mate. “No longer able to interbreed, the two populations drift apart, or are pushed apart by natural selection in different evolutionary directions” (p. 339) and thus over time evolve into different species. But the separation can also occur due to sexual selection.

He gives a fascinating example of this on page 339. He describes experiments done with two species of cichlid fish. The two species live together in Lake Victoria in Africa and are very similar, except that one has a reddish color and the other bluish. Under normal conditions, females choose males of the same color. In other words, there was no hybridization between the two colors in the wild, thus meeting the requirements for being considered different species. But when experimenters lit the fish in artificial monochromatic light so that they all looked dirty brown, the females no longer discriminated among the males and mated equally with both kinds of males and the offspring of these hybrids were fully fertile.

He also describes ring speciation using the example of the herring gull and lesser black-backed gull (p. 302). In Britain, these two kinds of birds don’t hybridize even though they meet and even breed alongside one another in mixed colonies. Thus they are considered different species.

But he goes on to say:

If you follow the population of herring gulls westward to North America, then on around the world across Siberia and back to Europe again, you notice a curious fact. The ‘herring gulls’, as you move around the pole, gradually become less and less like herring gulls and more and more like lesser black-backed gulls, until it turns out that our Western European lesser black-backed gulls actually are the other end of a ring-shaped continuum which started with herring gulls. At every stage around the ring, the birds are sufficiently similar to their immediate neighbors in the ring to interbreed with them. Until, that is, the ends of the continuum are reached, and the ring bites itself in the tail. The herring gull and the lesser black-backed gull in Europe never interbreed, although they are linked by a continuous series of interbreeding colleagues all the way around the other side of the world.

Dawkins gives a similar example of this kind of ring speciation with salamanders in the Central Valley of California.

Why is this interesting? Because it addresses a point that sometimes comes up with skeptics of evolution. They try and argue that there is a contradiction if we had evolved from an ancestor species that was so different from us that we could not interbreed with that species. Surely, the argument goes, doesn’t speciation imply that if species A evolves into species B, then must there be a time when the child is of species B while the parent is of species A. And isn’t that a ridiculous notion?

The herring gulls and salamanders are the counterexamples in space (which we can directly see now) of the counterargument in time (which we can only infer). What it says is that as descendants are produced, they form a continuum in time. Each generation, while differing slightly, can interbreed with its previous generation, but over a long enough period of time, the two end points of the time continuum need not be able to interbreed.

Thus it is possible for an organism to be intermediate between two species.

Coming back to the question of why we look so different if we all shared common ancestors so recently, it is likely that the kind of selectivity practiced by the cichlid fish has resulted in certain features being shared by groups that interbreed within a restricted domain bounded by distance and geography and culture, although the process has not become so extreme that we have formed into distinct species.

I apologize for boring those readers who had had a much more extensive biology education than I have because all these things which I have been writing about recently on evolution must be well known to them. But I find all this perfectly fascinating and novel.

POST SCRIPT: Amy Goodman in Cleveland

Award-winning journalist Amy Goodman, host of the daily, grassroots, global, radio/TV news hour Democracy Now!, is on a national speaking tour to mark DN!’s 10th anniversary and launch her second book with journalist David Goodman, Static: Government Liars, Media Cheerleaders, and the People Who Fight Back.

WHEN: Saturday, October 14th, 7:00-8:30 PM
WHERE: Student Center,
John Carroll University,
20700 N. Park Blvd (University Heights), Cleveland, OH
DESCRIPTION: Amy Goodman speaks at a free event at the Student Center. Book signing to follow. Members of Iraq Veterans Against the War will give a brief presentation before the talk, as part of their collaboration with the Uprise Tour.
TICKETS: Free
MORE INFO: See here for directions.

Why we look different despite having identical ancestors

In the previous post in this series, I reported on a paper by Douglas L. T. Rohde, Steve Olson, and Joseph T. Chang and published in the journal Nature that said that if we go back about 5,000 years, the ancestors of everyone on Earth today are exactly the same. This date is called the IA point, where IA stands for ‘identical ancestors’.

One question that will immediately arise in people’s minds is that if all our identical ancestors lived so recently, how is it that we look so different? If you take four people from China, Sri Lanka, Sweden, and Malawi, they are usually fairly easily distinguishable based on physical appearance alone, using features such as skin color, hair, facial features, etc. How could this happen if they all had identical ancestors as recently as 5,000 years ago?

The answer lies in the fact that while it is true that we all share the same ancestors, it does not mean that we all received that same genetic information from that common ancestral pool.

It is true that each of us gets exactly half our genes from our fathers and half from our mothers. But when we pass on our genes to our children, while each child gets exactly half from each parent, that does not imply that they get exactly one quarter from each grandparent. What is true is that on average each child gets one quarter of the genes from each grandparent.

The reason for this is because when a sperm or egg is formed, the genetic information (say in the egg formed in the mother) that goes into it undergoes a process of recombination in which the genes the mother obtained from her parents get mixed up before the transfer into the egg. It is thus theoretically possible, though unlikely, that a child will have zero genetic information from one of her four grandparents.

Furthermore, as we go down to the next generation, the average genetic information received by a child is now just one-eighth from any given great-grandparent. After many generations, even the average contribution of someone to each descendant approaches zero and it is not hard to imagine that some ancestors will have descendants who inherited none of their genetic information. In fact, as Rohde, Olson, and Chang say, “because DNA is inherited in relatively large segments from ancestors, an individual will receive little or no actual genetic inheritance from the vast majority of the ancestors living at the IA point.”

Furthermore, “In generations sufficiently far removed from the present, some ancestors appear much more often than do others on any current individual’s family tree, and can therefore be expected to contribute proportionately more to his or her genetic inheritance. For example, a present-day Norwegian generally owes the majority of his or her ancestry to people living in northern Europe at the IA point, and a very small portion to people living throughout the rest of the world.”

So even though we all have the same set of ancestors, the amount of genetic information received from any one ancestor will vary wildly from person to person.

As long as populations remained largely isolated, they could thus evolve different physical characteristics, although even a tiny amount of migration between populations is enough to create the early common dates of the MRCA (most recent common ancestor) and IA.

There are some factors that could shift those dates back further.

If a group of humans were completely isolated, then no mixing could occur between that group and others, and the MRCA would have to have lived before the start of the isolation. A more recent MRCA would not arise until the groups were once again well integrated. In the case of Tasmania, which may have been completely isolated from mainland Australia between the flooding of the Bass Strait, 9,000–12,000 years ago, and the European colonization of the island, starting in 1803, the IA date for all living humans must fall before the start of isolation. However, the MRCA date would be unaffected, because today there are no remaining native Tasmanians without some European or mainland Australian ancestry.

No large group is known to have maintained complete reproductive isolation for extended periods.

It seems to me that these results arguing for the fact that our most recent common ancestor lived about 2,000 years ago and that we all have the same common ancestors who lived just 5,000 years ago are pretty robust.

This has profound implications for origins myths and tribalism. Some people like to have a sense of racial pride by thinking that they represent ‘pure’ races. This research argues that this view is rubbish. None of us are ‘pure’. We are all cousins, and fairly close ones at that.

The most recent common ancestor of all humans living today

In order to find the date of the most recent common ancestor (MRCA) of all the people living today, Chang started out by constructing a simple mathematical model of population mixing. (See here for some background to this post.)

He assumed that the population is constant over time at some value N. He assumed that the generations are discrete and non-overlapping (i.e. mating took place only between males and females of the same generation). He also assumed that mating was random. In words, that there was equal probability of any one male in a generation to breed with any female of that same generation.
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