The Pheidole ants are an exceptionally diverse group with over 1,100 species. They’re also known as big-headed ants because their soldier caste has unusually large heads. Until now, we knew that a few of the Pheidole – just 8 out of 1,100 – can also produce supersoldiers, which are even larger than normal soldiers and have even more enormous heads. They use their outsized noggins to block their nest entrances against invading army ants.
Now, Ehab Abouheif has found that the supersoldiers are the result of a genetic programme that runs throughout the entire Pheidole dynasty. It’s likely that every single species in the vast group has the hidden ability to make this special caste. In fact, Abouheif managed to induce supersoldiers among species that don’t usually recruit them, with just a dab of hormone.
I wrote about this study for Nature, so head over there to read all the details. It’s a great evolutionary story.
If you think about fossils, you probably picture a piece of bone or shell, turned to stone and buried in the ground. You visit them in museums; some of you may even have found some. But your closest fossils are inside you, scattered throughout your genome. They are the remains of ancient viruses, which shoved their genes among those of our ancestors. There they remained, turning into genetic fossils that still lurk in our genomes to this day.
We’ve known about our viral ancestors for 40 years, but a new study shows that their genetic infiltration was far more extensive than anyone had realised. The viral roots of our family tree have just become a lot bigger.
Jellyfish may seem like simple blobs but some have surprisingly sophisticated features, including eyes. These are often just light-sensitive pits but species like the root-arm medusa have complex ‘camera’ eyes, with a lens that focuses light onto a retina. Not only are these organs superficially similar to ours, they’re also constructed from the same genetic building blocks.
Hiroshi Suga from the University of Basel has been studying the eyes of the root-arm medusa (Cladonema radiatum). His work strongly suggests that all animal eyes share a common origin, whether they belong to a human or an insect, an octopus or a jellyfish. The details may be different but they’re all under the control of closely related ‘master genes’ that themselves evolved from a common ancestor.
Sponges are among the most primitive of all animals. They are immobile, and live by filtering detritus from the water. They have no brains or, for that matter, any neurons, organs or even tissues. If you were looking for the evolutionary origins of animal intelligence, you couldn’t really pick a less likely subject to study.
With no neurons to speak of, these animals still have the genetic components of synapses, one of the most crucial parts of our nervous system. And their versions share startling similarities with those of humans.