Category: Science

Human origins

Theorists can move forward again – and the picture seems a little more complicated than we thought.

Where did we come from, and how? We’ve long thought in terms of an evolutionary ‘tree’, but our origins in Africa are more like a braided channel. This idea provides a better fit to the data.

Based on fossil evidence alone, studies of human evolution have long agreed that modern humans evolved in east Africa and radiated out from there. But with the development of cheap, fast and reliable DNA evidence from modern populations, and DNA from fossil teeth and bone samples, it’s becoming clear that theorists can move forward again – and the picture seems a little more complicated than we thought.

Human dispersion, events described in the article all took place in Africa – Image from Wikimedia

On 17th May, Ragsdale and others published a research paper in Nature; ‘A weakly structured stem for human origins in Africa’; their evidence suggests evolutionary connections in populations that were separated for a while before recombining. So instead of an evolutionary tree (which most people were expecting) it seems that our human past is more like a set of braided channels.

Previous views on human evolution proposed a tree structure (branching but not recombining). However, the new ‘weakly structured stem’ model fits the data better than a tree model. It also explains the diversity of genetic forms in modern human populations, and shows that there is no single place in Africa where humans ‘originated’. After this process within Africa, humans spread out as show in the map.

See also:

The Moon – and what else?

Let’s zoom in a little, that always helps…

The crescent Moon shines out in the evening of 23rd February, but there are three solar system objects in this image. After the Sun, the Moon is the second brightest object in Earth’s night sky.

The third and fourth brightest objects in our sky are present in this image. Can you see them? I doubt it, they are lost in the remaining glow of the sun as it sets. But if you know exactly where to look, you might see them.

The Moon and a couple of other things

Let’s zoom in a little, that always helps…

Can you see them now?

So, did you see them? No? They are there in plain view, but congratulations if you spotted them, it’s still not easy.

The third brightest object in our night sky is Venus, and you can see it near the bottom right corner of the photo – a little white dot. The fourth brightest object is Jupiter. It’s there to see as well, between the Moon and Venus, but a bit closer to Venus than to the Moon. See it now? (If you’re reading this on your phone you will need to enlarge the image.)

Later in the evening they are impossible to miss. The Moon is moving further away from this scene day by day, but Venus and Jupiter are getting closer to one another in the sky and are both very bright in a darker sky. Jupiter is also getting closer to the horizon and setting earlier and earlier as the days pass so if you want to see it, look in the next day or two. In April Jupiter will reappear in the morning sky before sunrise.

See also:

Watch Dr Becky’s Night Sky video segment for more detail (better yet, watch her entire video).

And for more detail on the three objects, take a look at Wikipedia’s articles on The Moon, Venus and Jupiter.

Making a fresh start

I sum these topics up on my Twitter profile as biology, web, science, technology, family, faith, history, and travel.

Having recently restarted blogging after a long pause, I’ve been thinking through how best to move forward – what should I change, what should I drop, and what should I keep?

Today’s post explains some of this, I’ll share what I’m doing and what I plan to do next. I’ll consider any comments you may leave, either here on the blog, or on Twitter or Facebook. But here’s how I see things right now.

Buy me a coffee

I’m offering everything I publish for free, but will always be delighted to receive a small gift, especially if you have sold or republished something (though even then it’s optional). Details are at coffee.scilla.org.uk .

Cruising the Gospel

This is a moribund blog that I’m in the process of restarting. I’m not sure yet whether to continue it in its present form, or to roll it into Journeys of Heart and Mind (JHM) as a topic in its own right. Currently I’m inclined to keep it as it is, and perhaps generate some PDFs from each book I complete. See it at gospel.scilla.org.uk .

Gateway

My Gateway site is mainly for my own use, but it’s full of links about Cirencester (my home town in England), local time and weather, some Christian links, local and national news, science and technology links and so forth. Some of you might like to take a peek. If so, head to gate.scilla.org.uk .

JDMC

JDMC stands for Jesus, Disciple, Mission, Church and is an introduction to Alan Hirsch’s Forgotten Ways. To learn more and download a copy to print (or read online), visit jdmc.scilla.org.uk . I need to update this booklet and plan to when I have time, unfortunately the web links in the PDF open OK, but using the browser to return take you back to the title page; I’ve been unable to fix this so far. If you open the links in a new tab you’ll be OK, but it’s easy to forget.

Journeys of Heart and mind

I intend to continue with this more or less as it stands. That means a mix of topics will appear here, articles about all of the things that motivate me as they occur to me (so in no particular order). I sum these topics up on my Twitter profile as biology, web, science, technology, family, faith, history, and travel. Others include photography, astronomy, spaceflight, archaeology and a few more. One thing I will add is a way of seeing just posts on one of these topics at a time, I think that will be useful; not everyone wants to see everything. You’re reading on this site at the moment.

Photos

I use Smugmug to display my photos and will continue with this, but I need to rearrange things in topic folders to make it more usable. Visit photos.scilla.org.uk to browse my all time favourites.

Twitter

My main Twitter account is ChrisJJ, but I have a second account, JHM. I haven’t used the JHM account for a long while, but might post tweets about faith topics there, and everything else on ChrisJJ. My mind is far from made up on this as there are quite a few pros and cons.

Emergence – INDEX

(See indexes on other topics)

Emergence is everywhere, and it’s a fundamental process that we see in this universe at every scale, from below atomic and molecular size to clusters of galaxies. Emergence is seen in the evolution of living forms, in landscape features, in the weather, the development of languages, cities, and engineering.

In the beginning – a field

The properties of the universe itself (whatever they may have been) seem to have resulted in the emergence of four fields, each with its own properties.

Part 2 of a series – Emergence

< Emergence – an introduction | Index | Combining atoms >

Fields underlie everything we’re familiar with in the universe in which we live. We know nothing about the universe at the time it began, though we know a surprising amount about the universe just a tiny fraction of a second after that beginning.

No, I’m not writing about a field with hedges around it, but a field as defined and understood by physicists. The first thing to exist in our universe was a field, quite possibly just a single field (or so I like to imagine). This is the second article on the topic of emergence, and you’ll see why later.

Various kinds of field (from Wikimedia Commons)

So let’s begin by thinking about the nature of a field. Physicists talk about several different fields – a gravitational field for example. In 1865 James Clerk Maxwell published ‘A Dynamical Theory of the Electromagnetic Field’ in which he explained that magnetism, electricity and light are all functions of a field. Fields are not particles, or forces (though they can and do give rise to these). Instead, a field permeates all of space. Right now you are exposed to the gravitational field and you are being acted on by the sun, the moon and the earth (and everything else in the universe). The pull these objects exert on you are in proportion to your mass and the mass of the distant object (let’s say the Sun) and by the distance between you. The strongest pull and the only one you will be aware of is the pull of the Earth, you’ll certainly notice it if you trip and fall over, or if you drop something. The Moon is not as massive as the Earth and is far away, so has much less pull. The Sun is much more massive than the Earth, but it’s also far, far more distant, and therefore pulls on you much less than the Earth does. These rules apply to every object in the universe, there is gravitational attraction between you and your cat (if you have one) also there’s gravitational attraction between you and the Andromeda galaxy. These attractions are very tiny as neither you nor the cat have much mass, and the Andromeda galaxy is exceedingly far away.

All of this can be quantified and a mathematical formula exists so that, given the masses of two objects and the distance between them, it’s easy to calculate the strength of the attraction.

So, where does emergence come in?

We don’t know how the universe began, or why, but we do know more or less when – almost 13.8 billion years ago. When the universe was still very new (if it makes sense to talk about time at all in the first picosecond (a billionth of a second), the still very tiny universe was filled by the gravitational field (as it still is today). This field became distinct from other fields repeatedly as the universe grew, giving rise to the electromagnetic field, then the weak field, and finally the strong field.

This represents the earliest event we might describe as emergence. The properties of the universe itself (whatever they may have been) seem to have resulted in the emergence of four fields, each with its own properties, four things that were not originally present. There’s probably little more to say about any of this, and the way I’ve portrayed it is speculative. But given these four fields, further steps of emergence can be discerned rather more clearly. And that’s something we’ll look at in another part of this series.

See also:
Part 2 of a series – Emergence

< Emergence – an introduction | Index | Combining atoms >