Category: evolution

This One Species Of Animal Proves That The Moon Can Affect Biological Evolution

“The combined effects of the Moon and Sun create two tidal bulges around Earth, yielding high tides and low tides twice daily. When the Sun, Earth, and Moon all align, we get spring tides: the highest high tides possible. Tidal extremes occur during new and full Moons, with twice the magnitude of intermediate-phase neap tides. One terrestrial animal, the grunion, has uniquely adapted to take advantage of this lunar-induced phenomenon.”

There’s a species of animal out there that is absolutely reliant on the Moon for its reproductive success. The grunion, found along the pacific and baja coasts of North America, mates in an interesting fashion. The females come onto shore during high tides, where they bury the lower halves of their bodies in the sand until they stick up vertically, where they lay their eggs. The males then wrap around them, depositing sperm in an attempt to fertilize them. Now, here’s the fun thing: the eggs must remain on dry land for 10-11 days to incubate, meaning that the grunion can only do this during the highest high tides: spring tides. 

Remarkably, because of our Moon’s properties and the combined tidal effects of the Moon and Sun, this enables the grunion to be an evolutionary success! Come get the full story here.

What Was It Like When The First Humans Arose On Earth?

“Approximately 300,000 years ago, the first Homo sapiens — anatomically modern humans — arose alongside our other hominid relatives. It is unknown whether we descended directly from Homo erectus, heidelbergensis, or antecessor, although neanderthals, which came slightly later at 240,000 years ago, most certainly came from Homo heidelbergensis. Modern speech is thought to have arisen almost as soon as Homo sapiens did.

It took 13.8 billion years of cosmic history for the first human beings to arise, and we did so relatively recently: just 300,000 years ago. 99.998% of the time that passed since the Big Bang had no human beings at all; our entire species has only existed for the most recent 0.002% of the Universe. Yet, in that short time, we’ve managed to figure out the entire cosmic story that led to our existence. Fortunately, the story won’t end with us, as it’s still being written.”

For those of you who haven’t been following, this is now part 30 of my series on “what was it like when…” where I’ve been chronicling our natural history, from before the Big Bang up through the present day. Next week’s will be the final installment of that series, as we’ll arrive at the present!

This edition takes us from 65 million years ago to just 300,000 years ago: the development of modern humans. Come take a read; it’s the story of us all.

What Was It Like When Mammals Evolved And Rose To Prominence?

“65 million years ago, 99.5% of the Universe’s history had already unfolded, and yet the ancestors of modern humans were no better developed than a modern-day lemur. Complex, differentiated animals had already existed for half-a-billion years, but it seems to be mere chance that led to the rise of an intelligent, technologically-advanced species like us. We do not yet know what secrets other planets hold as far as life goes, but here on Earth, the most remarkable story of all was just getting truly interesting.”

It was some 550-600 million years ago that life’s complexity exploded, at least in the fossil record, at the start of the Cambrian period. While that epoch marks 

the first complex, differentiated, macroscopic, multicellular, sexually-reproducing animals arising and dominating the oceans, life would go on to develop traits that were absolutely necessary for eventually giving rise to human beings. Animals developed spinal cords, four limbs, moved onto land, became warm-blooded, and more. Most importantly, many such creatures were able to survive enormous extinction events, enabling them to rise to prominence when a previously-occupied niche opened up.

It took half a billion years from the Cambrian explosion for mammals to rise to prominence, but after the big K-T extinction event, we were the most adaptable organism left. Here’s the story of how mammals like us evolved and came to dominate the Earth.

What Was It Like When Life’s Complexity Exploded?

“It is no doubt an oversimplification to state that horizontal gene transfer, the development of eukaryotes, multicellularity, and sexual reproduction are all it takes to go from primitive life to complex, differentiated life dominating a world. We know that this happened here on Earth, but we do not know what its likelihood was, or whether the billions of years it needed on Earth are typical or far more rapid than average.

What we do know is that life existed on Earth for nearly four billion years before the Cambrian explosion, which heralds the rise of complex animals. The story of early life on Earth is the story of most life on Earth, with only the last 550-600 million years showcasing the world as we’re familiar with it. After a 13.2 billion year cosmic journey, we were finally ready to enter the era of complex, differentiated, and possibly intelligent life.”

For the first few billion years of planet Earth, our world indeed had life occupying practically every niche we could imagine, but it was vastly different from the life we recognize today. Rather than complex, differentiated, multicellular organisms, all life in the early stages was single-celled and simple. Seemingly all at once, life’s complexity exploded some 550-600 million years ago during the Cambrian era. But this was no miraculous single event, but rather the culmination of many steps that worked together, in tandem, to make it all possible.

It took 13.2 billion years of cosmic evolution to give rise to the first megaflora and megafauna we find on Earth. Here were the critical steps that got us there.

Ask Ethan: How Fast Could Life Have Arisen In The Universe?

“How soon after the Big Bang would there have been enough heavy elements to form planets and possibly life?”

Making anything in this Universe takes time. After the Big Bang, there are a whole slew the Universe needed to take before rocky planets and life were possible. This includes the formation of atomic nuclei, neutral atoms, dense enough gas clouds to make stars, multiple generations of stars living-and-dying, and only then will the Universe be filled with the right ingredients to create rocky worlds and, potentially, life. But Earth didn’t come into existence until more than 9 billion years after the Big Bang, and these ingredients were around long before that. The heavy elements from the first supernovae could have made rocky, Earth-like planets very early on, but interestingly enough, it takes longer to form enough carbon to make life a reasonable possibility.

Let’s run through the Universe and find when life could have first evolved. The answer might be sooner than you think!

Astronomers Discover Exactly How Galaxies Die

“Our Milky Way contains large star-forming regions, mostly along its spiral arms, indicating stellar life. But other, mostly elliptical galaxies, stopped forming stars many billions of years ago. These galaxies are called red-and-dead, because they don’t have any hot, young, blue stars associated with recent star formation. Since the hottest, bluest stars burn through their fuel the fastest, an intrinsic red color is evidence that no new stars have formed for a long time.”

With hundreds of billions of stars burning inside a typical galaxy, it seems like a stretch to call any such object already “dead.” But if you aren’t actively forming new stars, and you don’t have the material in you to form new stars in the future, “dead” is exactly what you are, whether you realize it or not. We’ve had a number of theories, for a long time, as to why a galaxy could lose its gas and burn out, but for the first time, we’ve discovered one in the nearby Universe. Just 240 million light years away, the galaxy NGC 1277 has a unique set of circumstances:

  • it’s moving very quickly through the intra-cluster medium,
  • it contains an ultra-massive black hole at its core,
  • and both its stars and globular clusters are overwhelmingly red.

It looks as though it hasn’t formed new stars in some 10 billion years, making it the oldest, deadest galaxy we’ve ever seen up close!

Come learn all about it, and what it means for the deaths of galaxies, on this edition of Mostly Mute Monday!

Discovery Of A Young, Dead Galaxy Creates A Huge Puzzle For Astronomers

“When major mergers happen, stars form all at once, expelling the remaining gas that would be used for future generations of stars.

But one newly-discovered galaxy challenges that entire picture.

Younger spiral galaxies are smaller, bluer, gas-rich and less massive, in general.

Except, apparently, for MACS2129-1, which we see at a redshift of z=2.15, when the Universe was just 3 billion years old.

It is gas-poor and devoid of young, blue stars, and only half the physical size of the Milky Way despite being three times its mass.”

How do galaxies form and grow? The theory behind it is simple and straightforward. You start with a collection of normal-and-dark matter, the normal matter collects in the center, pancakes, and forms stars over time. A little later, more gas falls in, and the galaxy continues to form new stars over time. It’s only when a gravitational interaction or a major merger occurs that a galaxy goes from active to “dead and red,” in the form of a giant elliptical. At least, that’s the theory. But a new analysis of a very unusual galaxy, MACS2129-1, shows that despite being just 3 billion years old, it’s already “dead and red,” but it’s somehow still a spiral! With no evidence for a major merger and no conventional explanation for this otherwise, this young, dead galaxy creates a huge puzzle for astronomers.

What do we know so far? Come find out on this edition of Mostly Mute Monday!

We’ve Lost Sight Of The Most Important Rule In Debating Science

“In science it often happens that scientists say, ‘You know that’s a really good argument; my position is mistaken,’ and then they would actually change their minds and you never hear that old view from them again. They really do it. It doesn’t happen as often as it should, because scientists are human and change is sometimes painful. But it happens every day.”

There are many times throughout history that science – and scientists – have gotten it wrong. And there are many topics today that are quite polarized, from the Big Bang and evolution to vaccines, fluoridation, chemtrails and climate change. There are many public debates that play out, sometimes in nasty ways, surrounding all of these topics. Yet today marks the 97th anniversary of the most famous debate in the history of science, and there are important lessons from that momentum 1920 event that we seem to have forgotten today. If your goal is to convince other people that you’re right, don’t bother reading this. But if your goal is to arrive at a scientifically robust conclusion, and to make sense of the Universe based on that, read on.

The most important rule in debating science is to identify would take to convince us that our position is wrong. Come and find out what that’s all about!