Every third month Science direct lists the twentyfive hottest articles within a specific field of research. The present Hot topics list is based on number of downloads for each article during the full year of 2012. However, the list is still a good indicator if one wants to find out what’s hot in geosciences.
Based on the Science Direct list for 2012, I have compiled the three hottest topics within Earth and Planetary sciences, and these are:
Fresh water treatment/resources 6/25
Climate change/ocean acidification 5/25
Compared to the last published list the research focus of 2012 based on the most downloaded papers from Science Direct have changed somewhat. The most downloaded papers are now within Fresh water treatment/resources and three of these papers deal with reverse osmosis desalination. Reverse osmosis is one of the main technologies for producing fresh water from saline water and other wastewater sources. Fresh water shortage has become an important issue affecting the economic and social development in many countries, but there are still many challenges with reverse osmosis, as discussed by Kang & Kao (2012) and Pérez-Gonzaléz et al. (2012).
Papers on Ecology/Palaeoecology/Evolution and Climate change/ocean acidification have also attracted a lot of attention of the research community during 2012. The two subjects are tightly linked as exemplified by one of the most downloaded papers (nr 10 of 25), a review paper by Leslie Hughes from 2000: Biological consequences of global warming: is the signal already apparent?
Interestingly, the top downloaded paper within Earth and Planetary Sciences 2012 is a paper demonstrating the potential of microbial U(VI) reduction as an alternative technology to currently used physical/chemical processes for treatment and recovery of uranium in the nuclear industry (Chabalala & Chirwa, 2010). Perhaps this signals an increasing global need to find new methods in order to retreive natural resources that were previously considered to costly and technologically challenging?
To me, the 2012 hottest topics list signals increasing awareness within the research community that climatic and environmental changes, pollution and exploitation of natural resources presents new challenges in a world with increasing population pressure and demand of economic development!
Several years ago, while I was still working at Lund University, one of my colleagues Dr Johan Lindgren came to me one day with a microscope slide and asked me if I could help him check if there was anything in it. The only things we found were very small (ca 10-15 μm) spiny oval things, definitely not something palynological but most likely something organic of some sort.
Johan Lindgren showed me a paper by Mary Schweizer et al. (2007) which depicted small spiny cells from soft-tissue preserved inside bones from three different dinosaurs Tyrannosaurus rex, Triceratops horridus and Brachylophosaurus canadensis.
These cells were believed to be osteocytes, small star-shaped cells that reside inside bones and which can live as long as the organism itself and are capable of bone deposition and resorption.
The small spiny oval things that Johan Lindgren had in his slide definitely looked similar, although they did not come from a dinosaur but from a 70 million year old Mosasaur. Because this bone came from a marine reptile, a creature that had lived and died in the ocean, Johan Lindgren was determined to rule out that contamination from sea-sediment or other organisms was the source of the small spiny cells, and after years of research he finally published his results in the highly acclaimed open-access journal PLos One: Lindgren et al. 2011: Microscopic evidence of Cretaceous Bone Proteins. The photographic plate below from the Lindgren et al. (2011) paper shows the tiny spiny osteocytes still looking amazing after 70 million years!! 🙂
Fig. 1. from the Lindgren et al. (2011) paper showing the spiny osteocytes in photos A-F.
Pedomorphosis is an evolutionary process through which descendants end up looking like the juveniles of their ancestors. There are many known examples of this in the fossil record, e.g. amongst trilobites and amphibians.
Now, a study by Bhullar and colleagues in Nature show that birds skulls are morphologically similar to baby dinosaur skulls, indicating that birds are not only descendants of dinosaurs, but they have retained a juvenile morphology. One of the traits typical of baby dinosaurs is a large eye socket, and this is also typical for adult birds. While the morphology of baby dinosaur skulls were very different from those of their adults, baby birds have skulls that are virtually similar to adult birds. This has allowed birds to take a faster and more direct route to adulthood.
A palm tree previously thought to be endemic to arid central Australia is now believed to have been brought and planted there by the Aboriginies. Livistona mariae grows around the Finke River in the arid outback of central Australia. It is separated by ca 1000 km from another species, Livistona rigida, which grows in two river catchment areas in northern Australia, that of the Roper River and the Nicholson-Gregory River. This separation of the two species was believed to have occurred due to contraction of an ancestral population of Livistona as the Australian arid areas expanded from the mid-Miocene (ca 15 million years ago). Now the study by Kondo et al. (2012) instead shows, based on dna and population analysis, that L. mariae is most closely related to L. rigida from the Roper River, and that their separation is fairly recent with an estimate age between 32.000 and 15.000 years ago. Because there is no evidence of historical river connections between the Roper and Finke Rivers, the authors suggest that the most likely cause of the separation of L. mariae from the Livistona population at Roper River was via long-distance dispersal through opportunistic Aboriginal immigrants to central Australia. Being one of few indigenous eatable plants it makes sense the Aboriginies would bring their fruits with them as they colonized central Australia. You can also read about this study here 🙂
So, not all natural populations are natural after all? 😉
In an Early Edition Open Access article in PNAS “Origin of first cells at terrestrial, anoxic geothermal fields” Mulkidjanian et al. explore geochemical evidence for the origin of life on our planet. They find that all cells contain much higher amounts of potassium, phosphate and transition metals than any modern environments such as lakes, rivers and oceans, or for that matter reconstructed ancient such environments. They speculate that these higher levels of various elements are an inherited reflection of the inorganic environment in which the primordial cells were once formed, and use the geochemical composition to investigate suitable “cradles for life”.
Their results point to an origin of life, not in the oceans as we are used to, but in anoxic geothermal/volcanic fields on land, where the right geochemical conditions could be found. They argue that such anoxic geothermal/volcanic field on land could stay more or less unaffected by variations in the primordial climate for millions of years, long enough not only to form these “protocells” but also to sustain evolution of the first life forms.
In contrast to deep sea hydrothermal vents, which have also been suggested as “cradles of early life on Earth”, geothermal fields on land where subjected to weak solar light from the young sun which would probably be of benefit to the process.
It is a very interesting theory.
So perhaps life as we know it began on land, moved into the sea, diversified, evolved and then moved back on land billions of years later…
But how, when and why did the evolution process move into the sea?