Did Neanderthals Mate With Modern Humans?

When modern humans (Homo sapiens) migrated out of Africa around 140,000 to 100,000 years ago, it is likely that they ran into their more primitive cousins the Neanderthals (Homo neanderthalensis), who were already living in Europe. Both species probably evolved separately from the same ancestor, Homo erectus.

Did the two groups mate when they met? All we really know is that the Neanderthals disappeared about 28,000 years ago. Some scientists hypothesize that they were attacked or simply out-competed by modern humans; others claim that the two groups interbred, causing Neanderthal features to be absorbed into a larger population of modern humans.

Now there is new evidence that perhaps they did interbreed. Using modern DNA analysis techniques, scientists have determined that the Neanderthals have more genetic variations in common with present-day humans in Europe and Asia than with modern humans in Africa. These data suggest that interbreeding may have occurred if/when the two species met in Europe, before modern humans migrated out of Europe to Asia.

female gingko

So last quarter when discussing gymnosperms we talked about how there's biodiversity within the gymnosperms, specifically the variation between conifers (pinophyta), cycads (cycadophyta), gnetophytas, and gingkophytas. Interestingly, the gingkophyta is responsible for the gingko biloba, and it is the only species in its class etc. Essentially, it is its only living ancestor. Gingkos are really interesting because they can withstand a lot of trauma and live a really long time. However, another really interesting thing is that you have probably only seen male gingko trees. This is because the female gingko tree stinks hardcore. The fruit it produces smells like rancid butter, and because of this stench, a lot of people don't plant it. However, I was able to go on a trip to check out some female gingkos on a college campus in Portland Oregon, and for your interest here's a picture of what they look like. Unfortunately, they actually don't look any different than the male. The only way you can tell is by looking at the flowers, which are either clusters of little anthers on the male stem, or in the female's case, a small cluster of 2-3 tiny ovaries on the stem. A funny fact about these gingkos (there were two in front of the college's library) is that in the fall the fruit would smell so terrible, that they had to change the library's entrance to the other side of the building so that students and professors could avoid them.

Your inner fish

I just finished reading Neil Shubin's book 'Your Inner Fish.' It is a very easy and highly recommended read. We tend to focus on those areas where we have 'improved' on our fish-like ancestors (walking upright, doing pushups, inventing calculus etc) but what I found fascinating, and relevant to class today, was a discussion of olfaction (smelling) and how it's all been downhill since our aquatic past.

The human genome only contains about 23,000 protein-coding genes - which itself is an amazing fact. The other 98.5% of our genome consists of non-coding genes, regulatory sequences, introns and endogenous retrovirus sequences.

About 1,000 of those 23,000 protein-coding genes code for different odor receptors but less than half of them are functional in modern humans. Which says a lot about the importance of different senses in the evolution of humans from an aquatic ancestor (smell) to a terrestrial life (vision). Our evolutionary history is revealed in our genes.

Chytrid fungi

Available online today through PNAS early edition:

Dynamics of an emerging disease drive large-scale amphibian population extinctions
and
Enzootic and Epizootic Dynamics of the Chytrid Fungal Pathogen of Amphibians

UCSB has the Cliff notes press release: Studies Offer New Insights Into How Deadly Amphibian Disease Spreads and Kills

Scientists have unraveled the dynamics of a deadly disease that is wiping out amphibian populations across the globe. Chytridiomycosis is caused by a microscopic aquatic fungus called Batrachochytrium dendrobatidis (Bd) that attacks the skin of amphibians. The new findings, from two separate studies published in today's online edition of the Proceedings of the National Academy of Sciences (PNAS), suggest that infection intensity –– the severity of the disease among individuals –– determines whether frog populations will survive or succumb to chytridiomycosis. The research identifies a critical tipping point in infection intensity, beyond which chytridiomycosis causes mass mortalities and extinctions. UC Santa Barbara's Cheryl J. Briggs, professor of Ecology, Evolution and Marine Biology and the Duncan and Suzanne Mellichamp Chair in Systems Biology, is lead author of the second study and a co-author of the first study. Other collaborators from UCSB were Roland A. Knapp, a research biologist with the Marine Science Institute, and graduate student Tate S. Tunstall.

Cherie currently has ten undergraduates including at least 4 and possibly 5 CCS students working in her lab on a variety of projects from modeling and database work to PCR and genetic analysis to foodweb and mesocosm studies. So if any aspect of this work sounds interesting then you should contact either Cherie or Mary Toothman, her lab manager, directly.

Not forgetting of course how many ways this work ties into our lectures this quarter - Chytrid fungus (check); vertebrates (check); community interactions (check).

Octopusnuff

Huh? It's hard to make up a word that nobody has used on a webpage, ever. But apparently I did. I assume if you try that link in a few days/weeks/months? this page will then show up. [I checked a little over an hour later and this page was already there! I didn't realize google searched the web so continuously]. Anywho. I apologize to all cephalopod lovers for putting up the first video. But I believe it helps make three points:
1) You'll appreciate the selection pressure that led to video 2.
2) The evolution of shells and external skeletons led to so called 'adaptive radiations' in certain groups as they, temporarily, escaped their predators. This video shows the problems of the unarmored.
3) Remember one of the advantages of group living was being able to prey on larger or more difficult prey? I rest my case.



This next one is for the cephalopod lovers. You may have seen it before but it amazes me how the octopus mimics not just the colors but also the texture of the algae.

City of gonads

And whilst we are on the subject of oversized gonads (if you missed the museum visit that will be intriguing) here is the newly discovered 'city of gonads' jellyfish. Only a few millimetres wide with a cluster of gonads on top the jellyfish was found in the River Derwent in Hobart, Tasmania.

The new species has been named Csiromedusa medeopolis, meaning "jellyfish from CSIRO" and "city of gonads" and is so different from other jellyfish that it has been placed into a new family.

Ecology 'Midterm'

For those of you that missed it being handed out in class: The Ecology 'Midterm'