Science & Nature Archive

Monday, February 12, 2018

One More Darwin Day Link

Ape Skeletons

I just came across this article by Scott Solomon, so I thought I'd pass it on:

If you recall, Scott wrote the recent book, Future Humans, so he's in a good position to discuss recent human evolution. Go see what he had to say for Darwin Day.

Image Source: Houston Chronicle

Happy Darwin Day 2018

Darwin's BirthdayToday is Darwin Day, the 209th anniversary of Charles Darwin's birth. To reuse the same thing I've written for a few years now (origianlly here), Charles Darwin was "the man who presented evolution in such a way and with sufficient evidence that it became obvious that it was the explanation for how life developed on this planet. Others had ideas of transmutation before Darwin, and Alfred Russel Wallace even came up with a theory of natural selection very similar to Darwin's at around the same time, so it's apparent that humanity would have eventually recognized how evolution works. But Darwin's genius in presenting all the evidence for evolution in the way he did certainly gave the field a huge head start."

Although Darwin Day this year isn't getting anywhere the same attention as the bicentennial of Darwin's birth a few years ago, there are still Darwin Day events at various locations. If you want to see if there's anything near you, you can check out the list of events at DarwinDay.org. (I checked there and local calendars, but couldn't find anything for today in Wichita Falls.)

To celebrate Darwin Day on this site, I just posted a new entry today giving a concrete example of speciation:

Since the last Darwin Day, I've also created a section on this site highlighting some of my better writings on evolution, as a starting point for people who may not understand it very well. There are actually several entries there that are new since Darwin Day last year, so go check it out.

And here are a couple more entries I've written about Darwin that are appropriate for today.

Finally, here are links to external sites with good information about Darwin and evolution. The first is brand new this year, the next two are from the bicentennial celebration a few years ago, and the last is just a classic that's been around for years.

  • Oxford University Press - Darwin Day 2018 A great collection of links to articles and resources about Darwin.
  • Nature's Darwin 200 The prestigious journal has put together a collection of articles, editorials, news stories, and various other essays and features that have to do with evolution in general or Darwin in particular.
  • American Museum of Natural History's Darwin page Yet another good collection of information. This is from the exhibit that ran in the museum from 2005 to 2006.
  • The TalkOrigins Archive Has a bit more focus on the creation/evolution controversy rather than just straight science, and hasn't really had too many recent updates, but it is still very, very informative.

Evolution in Action - The Ongoing Speciation Event of Apple Maggot Flies

This entry is part of a collection on Understanding Evolution. For other entries in this collection, follow that link.


Apple Maggot FlyA little while ago, I came across a question on Quora, When gorillas and humans split from their common ancestor was there a 'new' individual of each new species born at that time?. Since other people had already discussed human evolution specifically, I decided to go with a more concrete example of an ongoing speciation event happening before our very eyes. Here's that answer, slightly edited.

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I'm going to give a concrete example - apple maggot flies. A few hundred years ago, there were no apple maggot flies, because there were no apples in the Americas. Apples weren't brought to the Americas until the 17th century. Now, there were obviously other types of trees and fruits in the Americas before that, and different types of insects that fed on them. One type of fruit bearing tree was the hawthorne, which was fed upon by hawthorne flies. You can probably see where this is heading.

Once Europeans brought apple trees to the Americas, there was a whole new potential food source for these flies. Some time in the early 1800s, some hawthorne flies began eating apples. They were still the same species as their relatives that ate hawthornes, without any drastic differences. They just had a few mutations that made them preferentially seek out apples as opposed to hawthornes. If anyone had put them in close contact with flies that still ate hawthornes, they wouldn't have had any trouble breeding.

Well, as the years went by, the flies that preferred apples began to get more and more distant from their hawthorne eating relatives. For one, since they were physically on apple trees more often than hawthornes, they mated more often with other apple eating flies. And since apples ripen earlier than hawthornes, the apple eating flies timed their emergence from their pupae to occur earlier in the year, introducing a separation in time, as well (obviously, this timing was based on genetic mutations, not conscious choice by the flies). Since each group of flies was more likely to mate with flies that ate the same type of fruit, any mutations that were appearing in the two different groups were more likely to remain in that particular group, and not be shared with the other group. So, the populations of apple maggot flies and hawthorne flies have been growing more genetically distinct.

Today, they are still classified as the same species, because flies from one group can still mate with flies from the other group to produce fertile offspring. But those hybrid offspring are less likely to survive because they'll have a mix of genetics from their parents, making them less specialized for eating either hawthornes or apples. The hybrids aren't completely doomed to dying without mating themselves, but because their chances are lower than non-hybrids, it further reduces the the gene flow between the two populations. If things continue as they are, these two populations will probably end up becoming two distinct species.

That's how speciation occurs. It's not something that occurs over a single generation. It's a process that takes many generations to complete. And the two incipient species are initially very similar. It's only many, many generations later, once each lineage has had a chance to evolve independently, that the two species start to show bigger differences.

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To answer the original Quora question regarding human evolution, millions of years ago when a certain population of apes gave rise to two different lineages - one that would eventually give rise to gorillas, and the other that would eventually give rise to chimps, bonobos, and us, it would have occurred in much the same way. At first there were two populations that were still the same species but just separated somehow. Once separated, they acquired unique mutations in each lineage. Eventually, many generations later, they were two distinct populations that could no longer interbreed - two separate, but closely related and very similar species. Only that speciation event would have taken longer than the current ongoing hawthorne/apple maggot fly event, because generations in apes are much longer than those of fruit flies.

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More Info:

Image Source: Wikipedia


Want to learn more about evolution? Find more at Understanding Evolution

Tuesday, December 5, 2017

An Early Christmas Present - Koch Snowflake Christmas Ornament 3D Printer STL Files

Koch Fractal SnowflakesI've had a 3D printer for a little while, now. While I mostly experiment with printing out various concept aircraft, I figured that for Christmas, I'd print a few Christmas ornaments. But with me being the nerd I am, I couldn't just print out any old random ornament. It had to be something a bit nerdier. So, after reading a post on Scientific American Blogs, A Few of My Favorite Spaces: The Koch Snowflake - A look at the most festive fractal, I was inspired to print a few tangible interpretations of the fractal. And I've shared the STL files below, for anybody else who might want to make them.

But first, here's a really cool animated gif from that Scientific American article, originally from Wikimedia Commons, showing the development of this fractal.

Koch Snowflake Fractal
Image Source: Wikimedia Commons, Credit: António Miguel de Campos

And here are the STL files. I've put a preview of each model. Clicking on the thumbnail will show a higher resolution image. To download the STL, use the actual download link.

Koch Snowflake 1 Preview Download Koch_Snowflake_1.STL
  
Koch Snowflake 1 Preview Download Koch_Snowflake_2.STL
  
Koch Snowflake 1 Preview Download Koch_Snowflake_3.STL

And here's a photo of the completed products.

Koch Snowflake Ornaments
Click to embiggen

Friday, October 13, 2017

Understanding Evolution - The Big Picture of Geologic Time

This entry is part of a collection on Understanding Evolution. For other entries in this collection, follow that link.


Geological Time SpiralThe Earth is old. Very old. You may have heard that it's 4.5 billion years old. But 4.5 may not sound like a huge number. The United States federal budget is nearly $4,000 billion. That's a bigger number than 4.5 billion, and it's something the government deals with on a yearly basis. So how old can 4.5 billion years really be?

This is the problem. Us humans aren't very good at dealing with really big or really small numbers. We're good at dealing with things on a human scale, whether it's size or age. When it gets to things that fall outside that range, we have a hard time wrapping our heads around it.

One of the better analogies I've seen is to imagine compressing 4.5 billion years down into one year, and then looking at how long things would take at that time scale. (It's not a big difference, but let's use a 365 day year, not a leap year.)

Let's start off by calibrating ourselves to something we're used to. Count to 1 second. That's 150 years - twice an average lifetime. If you're close to 40 like me, you only need to count to a third of a second to account for your entire life. Learning to walk, ride a bike, drive, my first job, my wedding day, watching my daughter grow up and graduate from high school. That all fits into 0.3 seconds in our compressed timescale.

For a slightly longer calibration point, let's go back to a big milestone - 1 AD. Well, maybe that's only a big milestone in hindsight since nobody at the time was actually changing their calendars, but it's still a number we can relate to - 2016 years ago. In our compressed calendar, that would have been a mere 14.13 seconds ago.

Keep those numbers in mind - 0.3 seconds for 40 years, 1 second for 150 years, or 14 seconds for 2000 years.

Okay, so now let's start going through the calendar. Keep in mind that a lot of these time periods and dates aren't known exactly, so in our 4.5 billion year year, they may have really been a few days or even weeks earlier or later.


Days 1 - 41, January 1 - Febrauary 10 (4.5 - 4.0 BYA)
Protoplanetary DiscFor the first 40 days or so, there wasn't much recognizable as the Earth as we know it. The cloud of dust and debris around the sun would have coalesced into the protoplanetary disc, with clumps forming and sticking together, until eventually some of the clumps got big enough to be early planets. Some time during this period, when the 'Earth' wasn't quite as big as it is now, it collided with another early planet about the size of Mars. This was a gargantuan impact, throwing out huge amounts of debris, some which coalesced to form the moon.


Days 41 - 57, February 11 - February 26 (4.0 - 3.8 BYA)
There were still a lot of asteroids out there at this point, so for roughly another two weeks, the Earth continued to get pummeled by these bodies, in what's known as the Late Heavy Bombardment.

Some time during those two weeks, the very first life got started. It would have been comparatively very simple, and certainly single celled. It would have been the type of life now known as prokaryotes - the archaea and bacteria. For the next 5 months or so, until August 3rd, these archaea and bacteria will reign supreme as the only type of life on the planet. Of course, they were evolving - replicating, mutating, and adapting, but they remained prokaryotes.

By the way, there was no oxygen in the atmosphere, yet. All the bacteria and archaea alive at this point are anaerobic.


Day 122, May 2 (3.0 BYA)

CyanobateriaCyanobacteria evolved. Forms of photosynthesis had evolved much earlier, but cyanobacteria evolved a new, more efficient method that created oxygen as a byproduct. Since oxygen is so reactive, at first any oxygen these cyanobacteria created would have reacted with iron to make rust. There was a lot of iron for the oxygen to react with, so for a while yet, there still wouldn't be much oxygen in the atmosphere. Until...


Day 163, June 12 (2.5 BYA)

The Great Oxygenation Event. Once all the free iron on Earth had reacted with the oxygen that cyanobacteria were making, there was nothing left to capture that oxygen, and it built up in the atmosphere very rapidly. But because oxygen is so reactive, it was actually poisonous to many organisms that hadn't evolved to handle it (antioxidants are still important even for us oxygen breathers - we don't want extra, unaccounted for oxygen running amock in our cells). This probably caused the first mass extinction on Earth (though it doesn't get as much press as other mass extinction events since no multi-cellular life was involved).


Day 215, August 3 (1.85 BYA)

YeastEukaryotes evolved. Okay, if you don't read about biology as much as me (or actual biologists), you may not know what a eukaryote is. They're the types of organisms that have a nucleus in their cells, and store all their DNA in chromosomes in that nucleus. They also have 'organelles', specialized little parts inside their cells with specific functions. One of the most famous is mitochondria, so often referred to as 'cellular powerhouses' for making the ATP that powers the rest of the cell. Amazingly, the most likely way this happened was symbiosis - a type of bacteria that would eventually become the mitochondria living alongside/inside some other species.

By the way, we're eukaryotes ourselves, but it will still be a while before we appear in this calendar.


Day 301, October 28 (800 MYA)

The first multicellular life appeared. Colonies of eukaryotes (and prokaryotes) would have been around before this, but these were the first eukaryotes to nudge past the distinction between a colony of clones and a group of clones considered a single organism.


Day 318 - 325, November 14 - November 21 (580 - 505 MYA)

Cambrian ExplosionThis was the famed Cambrian 'Explosion'. But it barely counts as an explosion even in our compressed calendar. Remember that in reality, this period lasted some 75 million years. It was during this time that complex multicellular life evolved, and branched out into many of the major groups that are still around. Granted, most of these organisms would have looked fairly primitive, but there at least would have been organisms big enough for a person to see with their naked eye (assuming you had a time machine), and recognizable as animals.


Day 326, November 22 (485 MYA)

Early FishThe first vertebrates with actual bones evolved, the jawless fishes. These jawless fish would eventually give rise to all the vertebrates alive today.


Day 330, November 26 (434 MYA)

The first land plants evolved. These first plants wouldn't have been particularly impressive, probably looking more like lichens. But over the coming ages, they would evolve more and more traits that benefitted their terrestrial lives.


Day 336, December 2 (363 MYA)

CarboniferousWell, it's the second day of the last month of our Earth history year. And by now, the Earth finally looks fairly recognizable. There are sharks and other fish swimming in the ocean, insects crawling around on land, feeding on plants with stems and leaves. It's round about this time that the first tetrapods took to the land. Sure, there are many types of plants and animals that haven't yet appeared, but if you went back in a time machine, you wouldn't feel like you were on a completely alien world.


Day 340, December 6 (320 MYA)
This was when some species of animals split into two, one of whose descendants would go on to become the synapsids (which includes us), and one of which would go on to become the sauropsids, which includes lizards and birds. But at the time, those two sister species would still have looked practically identical.


Day 343, December 9 (280 MYA)
The first seed-bearing plants evolved.


Day 347, December 13 (225 MYA)
The first dinosaurs evolved sometime around now, and just a few million years later (no more than a day or two in this compressed calendar), the first mammals also evolved. For the time being, both remained rather minor groups of animals, with therapsids and non-dinosaur archosaurs being the most dominant land animals for now.


Day 349, December 15 (200 MYA)
A mass extinction occurred, killing off most of the synapsids. After today, the dinosaurs would diversify and come to dominate the planet. Mammals still remained small.


Day 353, December 19 (155 MYA)
Archaeopteryx - Berlin SpecimenThis may not be the most significant event in the history of the planet, but it's one I'm interested in personally - Archaeopteryx evolved. And since Archaeopteryx was either one of the first birds, or a very close relative of the first birds, it was right around this time that birds evolved.


Day 355, December 21 (130 MYA)
Flowers evolved. Just think about that. We're two thirds of the way through December, and the first flowers are just now appearing.


Day 360, December 26 (65 MYA)
K-Pg Impact EventA gigantic asteroid collided with the Earth, causing a massive explosion and cataclysmic devastation on the planet. With only a few exceptions, no land animals over 50 lbs survived. All of the non-bird dinosaurs went extinct, though plenty of bird species were wiped out, as well. In fact, species from pretty much every major branch of life went extinct - mammals, marine reptiles, insects, plants, fish, all the pterosaurs, etc. In the wake of this devastation, the remaining mammals would diversify to become the dominant large animals on land.


Day 365, December 31, 12:00 noon (6 MYA)
ProconsulOn noon of the last day of our compressed year, an ancient species of ape split into two species. The descendants of one of those species would remain in the forests, and eventually give rise to chimpanzees and bonobos. The descendants of the other would gradually move out to the savannahs, eventually giving rising to us - but not for a little while, yet.


Day 365, December 31, 11:48 pm (100,000 YA)
Modern humans appeared about a quarter of an hour till midnight. This gets a little into semantics on which of our ancestors you're willing to say are 'human' vs. 'pre-human', so give or take a few minutes here to allow for the fuzziness of this transition.


Day 365, December 31, 11:58:50 pm (10,000 YA)
The first human civilizations started some time around now.


Day 365, December 31, 11:59:25 pm (5,000 YA)
Early WritingThe famous ball in times square is about halfway through its drop, and humans have just developed writing.


Day 365, December 31, 11:59:46 pm (2,016 YA)
The year 1 AD.


Day 366, January 1, 12:00 midnight (Now)
And now, at the stroke of midnight, we've reached the present day.


So, it may seem like things really started accelerating there towards the end of the year, but that's mostly due to our own bias of being more interested in those particular events, and the bias of the geologic record in containing more younger fossils and artifacts than older ones. Just as much was happening 100 million years ago as a few thousand years ago, just without us humans around to see it.

And even if it seems like a lot was happening in a few mere days, recall what these time scales really mean. On this condensed calendar, a human lifespan is less than a second. The last two millenia were a mere 13 seconds, and all of humanity's time on Earth is no more than a few minutes*. Start counting out seconds, trying to imagine entire generations passing with each count, to get an idea of just how vast these timescales are. Then, try to imagine continuing that count for a whole day, and just how much time that really represents. And then, think back to what you were doing a year ago, and how many seconds have passed since that moment, and maybe you'll start to get an idea of how long 4.5 billion years really is.

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*To be fair, most species haven't been around very long on a geologic scale, even if humanity is a bit on the young side. Species last maybe a million years or so before either going extinct, or evolving into something else. Life is constantly changing and adapting.

Image Sources:


Want to learn more about evolution? Find more at Understanding Evolution.

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