Bill writes:

Dear TWiEVO folks;

It is a beautiful spring day here in Berkeley, CA. 75F/24C, 35% humidity, cooling to a more typical 65F/18C later in the week, with a chance of rain in a few days.

It might be interesting to do a TWiEVO on the evolution of life from beginning to formation of multi-cellular organisms. This thought was sparked by the following article, which talks about life at a time when nothing modern could have lived. (Well, maybe that is not strictly true as the anaerobes that live in deep rock pores presumably could have lived. – a facinating topic in its own right:

Bubbles may have sheltered Earth’s early life

Science News

Magazine issue: Vol. 189, No. 3, February 6, 2016, p. 12

My abstract:

Pockets of gas trapped along ancient shorelines gave microbes a cozy place to call home about 3.2 billion years ago, scientists suggest December 4 in Geology. Such a snug hideout could have shielded microbes from ultraviolet radiation not only on Earth, but perhaps on Mars as well.

Earth was a tough place to live a few billion years ago. No oxygen in the atmosphere meant no ozone, and therefore no protection from the sun’s ultraviolet rays, says study coauthor Alessandro Airo, a geobiologist at the Free University of Berlin in Germany.

Still, microbes found a way to survive. In many places around the world, these organisms glued sand and cells together, forming slimy carpetlike biofilms, or mats, underwater. Iron dissolved in the water could have screened out radiation, Airo says. During low tide, “surface microbes might get zapped by UV and die,” he says, but communities of microbes living below them may have thrived.

Underlying scientific publication:

Homann et al. Evidence for cavity-dwelling microbial life in 3.22 Ga tidal deposits. Geology. Published online December 4, 2015. doi: 10.1130/G37272.1.

Bill (William) Johnston

Berkeley, CA

Bill writes:

Dear TWiEVOers

Perfect spring weather here in Berkeley: 67F/19C,  light breeze, a bit more humid than normal (72%) as there is some rain expected tomorrow.

I am sure you have or will see this but here it is anyway.

” The most characteristic feature of Darwin’s finches is the diversification of beak morphology that has allowed these species to expand their utilization of food resources in the Galápagos archipelago. A team of scientists from Uppsala University and Princeton University has now identified a gene that explains variation in beak size within and among species. The gene contributed to a rapid shift in beak size of the medium ground finch following a severe drought. The study is published in Science.

Read more at:

More information: “A beak size locus in Darwin’s finches facilitated character displacement during a drought,” Science, DOI: 10.1126/science.aad8786

Bill (William) Johnston

Berkeley, CA

Anthony writes:

The smallest avian genomes are found in hummingbirds.


It has often been suggested that the genome sizes of birds are constrained relative to other tetrapods owing to the high metabolic demands of powered flight and the link between nuclear DNA content and red blood cell size. This hypothesis predicts that hummingbirds, which engage in energy-intensive hovering flight, will display especially constrained genomes even relative to other birds. We report genome size measurements for 37 species of hummingbirds that confirm this prediction. Our results suggest that genome size was reduced before the divergence of extant hummingbird lineages, and that only minimal additional reduction occurred during hummingbird diversification. Unlike in some other avian taxa, the small amount of variation observed within hummingbirds is not explained by variation in respiratory and flight-related parameters. Unexpectedly, genome size appears to have increased in four unrelated hummingbird species whose distributions are centred on humid forests of the upper-tropical elevational zone on the eastern slope of the Andes. This suggests that the secondary expansion of the genome may have been mediated by biogeographical and demographic effects.

Bill writes:

Dear TWiEVO-ers;

Re the most recent TWiEVO, apparently credible DNA has been extracted from ancient horses preserved in permanent-frost :

” In June 2013, a group of researchers announced that they had sequenced the DNA of a 560–780 thousand year old horse, using material extracted from a leg bone found buried in permafrost in Canada’s Yukon territory.[25] In 2013, a German team reconstructed the mitochondrial genome of an Ursus deningeri more than 300,000 years old, proving that authentic ancient DNA can be preserved for hundreds of thousand years outside of permafrost.[26]

William Johnston

Berkeley, CA

PS It is breezy with puffy clouds and 62F/16.6C here in Berkeley.

Sofie writes:

Dear Twievos, Dr. Racaniello and Dr. Elde

Thank you for another great podcast celebrating science and the wonder of nature.

I’m an MD living in Denmark slaving through my PhD in epidemiology – so not much of a lab person unfortunately.

You don’t have to read this email or post it anywhere I just want to suggest a researcher you might want to try to bring on the show some day – if possible. I’m a big fan of professor Eske Willerslev (see links below). He has published a bunch in Science and Nature on evolution and he is – on top of a great researcher – fantastic at communicating his results and very down to earth.

I know – like you and every other accomplished researcher – he is extremely busy. But if one of you should ever happen to come to Denmark or he should come to the states you could consider contacting him.

He doesn’t know much about viruses but I know he is interested in trying to sequence ancient “microbioms” (bacteria, fungus and virus) of ancient people. He has lately published data where he found Y. Pestis DNA in samples from bronze age homo sapiens. (

But Eske is really just a great guy to talk to about the evolution of homo sapiens and how to sequence ancient DNA.

Fond Regards

Robert writes:

I haven’t read the paper yet but saw this come by and thought of you guys, especially after listening to the pigeon podcast. Maybe this is run of the mill evolutionary sequencing work but it’s pretty darn cool to an engineer like me:

The origins of giraffe’s imposing stature and associated cardiovascular adaptations are unknown. Okapi, which lacks these unique features, is giraffe’s closest relative and provides a useful comparison, to identify genetic variation underlying giraffe’s long neck and cardiovascular system. The genomes of giraffe and okapi were sequenced, and through comparative analyses genes and pathways were identified that exhibit unique genetic changes and likely contribute to giraffe’s unique features. Some of these genes are in the HOX, NOTCH and FGF signalling pathways, which regulate both skeletal and cardiovascular development, suggesting that giraffe’s stature and cardiovascular adaptations evolved in parallel through changes in a small number of genes. Mitochondrial metabolism and volatile fatty acids transport genes are also evolutionarily diverged in giraffe and may be related to its unusual diet that includes toxic plants. Unexpectedly, substantial evolutionary changes have occurred in giraffe and okapi in double-strand break repair and centrosome functions.

Anthony writes:

I only listened to the recent TWiEvo once, so perhaps I heard wrong.  I thought that you said that parasitic wasps deposit larvae.  They lay eggs, as may be seen in the image at TWiV #179:

BTW, the parasitic wasps were a focus of Darwin’s:

I cannot persuade myself that a beneficent and omnipotent God would have designedly created the Ichneumonidae with the express intention of their feeding within the living bodies of Caterpillars, or that a cat should play with mice.”

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