Fossil Friday: Thar She Blows; Whale evolution.

Thar She Blows: Evolution of whales!

by Rich Feldenberg

 

Welcome back to Fossil Friday.  The evolution of the cetacean group (marine mammals like whales and dolphins) is one of the coolest and most beautiful demonstrations of a clear link of fossil evidence from primitive forms to modern forms with many transitional fossils present.  

Whales, are of course, mammals and descended from air breathing land vertebrates.  All tetrapods descended from lobe finned fish (see my Tiktaalik post).  From there they diversified into amphibians, reptiles, mammals, and birds.  Some of the groups of reptiles (like the great marine reptiles during the age of the dinosaurs), and mammals (like the whales) returned to the sea many millions of years later.  Based on molecular genetics studies, the closest living land mammals to the whales is the hippopotamus.  

Cute little Pakicetus was one of the earliest known proto-whales.  These hoofed footed mammals were alive about 50 million years ago.  Based on bone structure of the skull around the auditory region, they fit into the cetacean group, but were not thought to be good swimmers.  Good swimmers in the family would come later!

It is thought that changes in the regulation of genes such as Sonic Hedge Hog (Shh) and Tbx4 may have been important in the loss of the hind limbs in the cetaceans.  By affecting when and how genes are expressed, major changes in structure can be made due to relatively small genetic changes. It is also pretty amazing to see the embryology of modern whales also betrays their ancestry. For example, in the whale fetus the nostrils start out in the usual position for a mammal, but as the maxillary bones grow to huge proportions this forces the nasal bones to the top of the skull. This type of evolutionary effect is called allometry and refers to a change in body parts due to changing the growth rate of different parts in relation to one another.

Over time the cetaceans evolved their characteristic echolocation apparatus, as well as, the development the blow hole from nostrils that were originally forward on the face.  Today, cetaceans are beautifully adapted for life in the oceans.

References and a cool video to watch:

1. Whale evolution Wikipedia:

https://en.wikipedia.org/wiki/Evolution_of_cetaceans

2. Animated video of whale evolution. This is pretty cool, check it out.

http://ocean.si.edu/ocean-videos/evolution-whales-animation

3. Sonic hedge hog:  Wikipedia

https://en.wikipedia.org/wiki/Sonic_hedgehog

4. Tbx4:   http://dev.biologists.org/content/130/12/e1205.full

Origins Sunday: Early life liked it salty!

Cool link below describing research that shows how a certain set of 10 amino acids will fold when exposed to high salt concentrations, like those found naturally in certain regions of the early earth.  This may have allowed proteins to be functional before the cellular machinery to fold proteins had yet evolved.  Our earliest ancestors may have been halophiles (salt lovers).  Unfortunately, many of us retain that salt loving trait, and perhaps that’s why I love pizza so much?!? – craving the salt that my Archean ancestors loved so!

http://www.sciencedaily.com/releases/2013/04/130405064027.htm

Origins Saturday: Origin of America!

by Rich Feldenberg

Today, in honor of Independence Day weekend, we will do something slightly different with Origins Sunday.  For one thing we are temporarily converting it into Origins Saturday so it can coincide with Independence Day.  As a critical thinker it is important not to be rigid in your thinking, but to remain flexible so as to adjust to ever changing conditions – but that’s a topic for another time.

In this episode of Origins, we also diverge from the usual topic of life’s origins, and instead will show the origins of the North American continent, and the place we now call The United States of America.  Today is the 239th birthday of the USA (happy birthday America), but the land mass that we live on is much older than that, and has been apart of other supercontinents in the distant past.  Below, you can see the distribution of the present day continents placed over the supercontinent Pangea.

Pangea was a fully formed supercontinent about 299 million years ago, and began to break apart due to continental drift, around 200 million years ago.  That was during the Permian Period when the dry land was ruled by primitive reptiles and the mammal-like reptiles (of which, included our ancestors at that time).   The mammal-like reptiles could be considered as Proto-mammals, with features of both reptiles and mammals.  Check out below:  aren’t they cute, but be careful they bite!

On Pangea, the inhabitants of the time could move across the continent, at least in principle.  The interior may have been very dry and inhospitable to many forms of terrestrial life at the time.   One line of evidence for the formation and breakup of the supercontinent is the distribution of fossils found in various locations.  Their pattern shows that before the breakup there were the same creatures living on both sides of fault lines, in a non-random distribution.

Before America came to its present location it drifted across the globe and had been in physical contact with what would become Africa, Europe, and South America.  Due to plate tectonics it is continuing to drift today, and in another 200 million years the map of the world will look vastly different from the one we are used to seeing.  This should remind us that we are all truly global creatures.  Our ancestors have lived all over this planet, from the ancient seas, to many of places among the land masses.  Have a fun and safe July 4th weekend!!

References and further reading:
1.  “Pangea | Supercontinent”, The Encyclopedia Britannica; http://www.britannica.com/place/Pangea

2. “Nine of Your Relatives That Ruled Before Dinosaurs”,  Tor.comhttp://www.tor.com/2014/02/05/nine-of-your-relatives-that-ruled-before-dinosaurs/

Fossil Friday: Oldest fossils on earth!

Modern day stromatolites in Sharks Bay, Australia

Welcome back to Fossil Friday.  Today I’m linking to a 2013 article in LiveScience, that reports on 3.5 billion year old fossil bacteria.  These Australian fossils are among the oldest fossils yet discovered.  In life, they seem to have existed in shallow waters and may have been a variety of photosynthetic bacteria.  Not only did life arise very early in the history of our planet, but oxygen producing organisms appear to have gotten their start very early, as well.  The bacteria are visible as fossils because they form structures called stromatolites.  There are still bacterial stromatolites alive today in Australia.  They were probably common in the early oceans, but rare now due to predators that would easily gobble them up!

Oldest Fossils on Earth

Fossil Friday: Dickinsonia

by Rich Feldenberg

Welcome to the long forgotten Ediacaran Period (635-542 Million years ago) in the Precambrian.  An assortment of unusual and fascinating fossils have been found dating to this time period, when multicellular life was just getting large enough to make good fossil imprints.  It is sometimes known as “The Garden of Ediacaran” because it is thought that at this early stage of animal evolution most creatures were basically filter feeders, and no major predation had yet developed (including the tools used by predators such as teeth, eyes, or sophisticated brains).  In that sense it may have been a very peaceful and “innocent” chapter in the history of life, before an evolutionary arms race between predator and prey began in the Cambrian and continues on to this day.

One common fossil found in rocks of this age is that of Dickinsonia.  This little guy was round shaped with a bilateral symmetry – something that shows some level of sophistication from the even earlier radially symmetric ancestors.  It seems to have had a head-end and a tail-end and was divided into segments.  It is not clear what kind of animal Dickinsonia really was, and there is a great bit of controversy in the scientific community in regards to its proper placement on the tree of life.  It seems to have been capable of movement over the ocean floor, as there have been fossilized tracts found that are thought due to its movements.   It may have belonged to a phyla that went extinct by the end of the Ediacaran period, or alternatively it may be related to modern day creatures.  Some experts have speculated that it is related to modern day jellyfish and some even think it may be related to animals that eventually became vertebrates.  Others have even gone so far as to say that it was not an animal at all, but part of a short lived, and ultimately unsuccessful evolutionary experiment in some type of multicellular life form that went extinct half a billion years ago.  What ever Dickinsonia was it made beautiful fossils!