Life without sex can have its downsides

Do not let the title of this post allow your imagination to run wild.  You are on a slippery path, dear reader!

The sex that this post is about is not about humans or porn.  Ditch that thought.  But, wait, don't go away.  You can always watch porn later.  Read this post, which will do you good ;)

Sex is nearly ubiquitous, but it hasn’t been easy to explain its ubiquity. ...
While sex may be a bit of a mystery to us all, it has been the grand enigma of evolutionary biology for decades.

No, it is not about humans.  It is about bananas and corn.  No, I am not using them as metaphors but literally.

Of the important global crops, the banana is the most genetically uniform. A single cluster of nearly identical genotypes, the Cavendish subgroup, nearly monopolizes the world’s banana groves and banana trade. In contrast to the riotous rainbow of genetic diversity that lends sustainability to natural plant and animal populations, the world’s banana industry has the stability of an upside-down Egyptian pyramid balanced on its tip.
That fact leads to another superlative: The commercial banana is the world’s most endangered major crop. The future of the intercontinentally traded banana was once, and is again, precarious.

Talking about the precarious state of bananas is not new here.  But, in that post, I didn't go into the importance of sex.

What about sex and bananas?

Domesticated banana plants are self-copying machines.

With the emergence of the 20th century, the confluence of the Industrial Revolution with plantation agriculture led to the propagation of a single globally favored banana genet (descended from a single instance of sperm-egg fusion) for export from the tropics to waiting markets in the industrial north.

So, why would I want you to think about sex when eating a banana?

Because most important crops reproduce only by sexual seed, they cannot be clonally propagated. Not surprisingly, the genetic variation generated by sexual reproduction is an obstacle for many folks looking to deliver a better crop product. For the past quarter century, some plant biotechnologists have argued that future crops should follow the banana, dispensing with sex entirely. Specifically, they are titillated by the idea of varieties that replicate the maternal plant via reliably uniform, asexual, apomictic seed.³ One proposal is that the plant breeders would maintain sexually fertile lineages that, when crossed, would create apomictic offspring. A second approach would be to genetically engineer plants to be apomictic. The seeds produced by either method could be delivered to farmers, who benefit from the crop’s uniformity.

So, is it a good thing, or a bad thing, to dispense with sex entirely?

It depends.

The explanation for sex isn’t straightforward. Sex is a hassle. To reproduce without sex, an organism can dedicate a cell toward creating a new individual, pump it up with some resources, and eventually set its baby free. The organism that uses sex to reproduce has a greater challenge; it has to create gametes that have to find other gametes. The process of seeking or attracting those other gametes typically involves allocation of resources to special structures and, in the case of animals, allocation of resources and time to special behaviors.

Why not let technologists work it out in the lab?

The original Cavendish-resistant Panama disease culprit has now been named Race 1. Panama disease fungi have evolved; the Race 1 genotypes are being replaced by one known as Race 4, which first appeared in 1965. Cavendish has no resistance to Race 4. The evolutionarily new and improved Panama disease organism has wiped out thousands of Cavendish acres in Southeast Asia. Since then it has been identified in the Pacific, Australia, Africa, and the Middle East. Worse yet, in 2011 Cavendish bananas in India started succumbing to what appears to be a new genetic variant of Race 1. The bad news is that Cavendish is fully sexually sterile.

Sex might be a hassle, messy, and needing resources.  But, it is key to survival. 

Source

Geography at birth

For a while now, I have been blogging about the (mis)fortunes that come our way just because of our parents.  Who we are born to makes a huge difference in life.  Every time I blog along those lines, the frequent (and now the only) commenter, and others have disagreed with me.  (Check this out, or this, for instance.)

I have also blogged in plenty about luck. Dumb luck.

Thus, I have never really cared much for people bragging about how they made it all by themselves.  Not that he brags, but consider Bill Gates.  It is not as if he created his fortunes after growing up in the projects.  I was not born a Dalit and my father was not a manual scavenger.  The truly rags to riches, rising from the utterly disadvantaged, is a rare exception.  Most of us have only built upon the accident of birth.

To quite some extent, the cosmic dice rolled in our favor, which is why you and I are interacting here.

I started thinking as a social scientist on the role of circumstance and luck in how lives turn out. It's a sobering experience to realize just how many variables are out of our control

Yep.  That's what I have been saying for a long, long time.

What about intelligence and hard work? Surely they matter as much as luck. Yes, but decades of data from behavior genetics tell us that at least half of intelligence is heritable, as is having a personality high in openness to experience, conscientiousness and the need for achievement—all factors that help to shape success. The nongenetic components of aptitude, scrupulousness and ambition matter, too, of course, but most of those environmental and cultural variables were provided by others or circumstances not of your making.

Choosing your parents well has given you one hell of an advantage, dear reader!

Michael Shermer wraps up his column--his 200th for the Scientific American--with this:

There should be consolation in the fact that studies show that what is important in the long run is not success so much as living a meaningful life. And that is the result of having family and friends, setting long-range goals, meeting challenges with courage and conviction, and being true to yourself.

Ahem, I have been saying this, too, for the longest time.  Damn, I am good!

My genetic journey, from Tanzania to Eugene, via India

Nearly three years ago, I authored this column in the paper here, in which I described how the visit to Tanzania was a homecoming for me:. 

Tanzania offers a compelling argument for why it is home to humans — going back to hominids, who were human-like precursors to our kind. The evidence, in this case, includes the well-preserved footprints of hominids in northern Tanzania, estimated to be 3.75 million years old.

There was still something missing even after that trip, which I understood much later--to go beyond the theoretical argument, and get evidence of how I came to be from that African origins.

A few weeks ago, when I was reading an essay, I came across a reference to the Genographic Project, and I decided to participate in that as a kind of a belated birthday gift to myself (yes, I paid for my own gift, thank you very much.)  Because there was that payment to be made, I asked only for the "male" side of the history--after all, only males can get the male side of the story, given the Y chromosome.  Some time later, I would gift myself with the female side of the past as well.

Today, I got the results of the DNA analysis, which tell a story of my origins from Africa.  The genetic map shows how I got to India, all the way from Africa:

Compared to the tens of thousands of years that it took for the geographic movement out of Africa to India to happen, I came over to Los Angeles in 1987 after a mere day of air travel.  Perhaps those early ancestors would not have even dreamed about such a possibility?

Anyway, the report notes:

The man who gave rise to the first genetic marker in your lineage probably lived in northeast Africa in the region of the Rift Valley, perhaps in present-day Ethiopia, Kenya, or Tanzania, some 31,000 to 79,000 years ago. Scientists put the most likely date for when he lived at around 50,000 years ago. His descendants became the only lineage to survive outside of Africa, making him the common ancestor of every non-African man living today.

The place I visited in Tanzania was really, really, close enough to be the real, old, ancestral home--the home before Pattamadai, Sengottai, and Neyveli that I have often blogged about.

Anyway, from Tanzania (as I imagine the home!):

Your ancestors, having migrated north out of Africa into the Middle East, then traveled both east and west along this Central Asian superhighway. A smaller group continued moving north from the Middle East to Anatolia and the Balkans, trading familiar grasslands for forests and high country.

And then from there,

Your next ancestor, a man born around 40,000 years ago in Iran or southern Central Asia, gave rise to a genetic marker known as M9, which marked a new lineage diverging from the M89 Middle Eastern Clan. His descendants, of which you are one, spent the next 30,000 years populating much of the planet.

Getting close to India ...

The man who gave rise to marker M20 was born in India or the Middle East. Your ancestors arrived in India around 30,000 years ago and represent the earliest significant settlement of India. For this reason, haplogroup L (M61) is known as the Indian Clan.
Although more than 50 percent of southern Indians carry marker M20 and are members of haplogroup L (M61), your ancestors were not the first people to reach India; descendants of an early wave of migration out of Africa that took place some 50,000 to 60,000 years ago had already settled in small groups along the southern coastline of the sub-continent.

So, there!  Everything else was easy, it seems like.

About that Y chromosome itself?  It is alive--through my nephews, now it is in Australia!

I was excited when I saw these elephants at Mikumi National Park, Tanzania. 

SAT scores related to bathrooms in the house?

Greg Mankiw:

The NY Times Economix blog offers us the above graph, showing that kids from higher income families get higher average SAT scores.

Of course! But so what? This fact tells us nothing about the causal impact of income on test scores. (Economix does not advance a causal interpretation, but nor does it warn readers against it.)

This graph is a good example of omitted variable bias, a statistical issue discussed in Chapter 2 of my favorite textbook. The key omitted variable here is parents' IQ. Smart parents make more money and pass those good genes on to their offspring.

Suppose we were to graph average SAT scores by the number of bathrooms a student has in his or her family home. That curve would also likely slope upward. (After all, people with more money buy larger homes with more bathrooms.) But it would be a mistake to conclude that installing an extra toilet raises yours kids' SAT scores.

It would be interesting to see the above graph reproduced for adopted children only. I bet that the curve would be a lot flatter.

Hmmm..... IQ and genes. Controversial, right? Of course. Because this is an unsettled issue in science. Conor Clarke remarks that "the vaguely deterministic suggestion that smart parents "make more money and pass those good genes on to their offspring" is a laughably crude description of how real life works" and cites a study by Richard Nisbett and notes that:

children born to wealthy parents and raised by downscale families have almost exactly the same IQ range as children born to downscale parents and raised by wealthy families. Nisbett uses this to make what I thought would have been an entirely uncontroversial point -- namely, that "both genes and class-related environmental effects are powerful contributors to intelligence"

Shall watch out for the next round of this discussion :-)