50 Million Years of Whale Evolution

50 Million Years of Whale Evolution The basic theme of whale evolution is the development of large animals from much smaller ancestorsand nowhere is this more evident than in the case of multi-ton sperm and gray whales, whose ultimate forebears were small, dog-sized prehistoric mammals that prowled the riverbeds of central Asia 50 million years ago. Perhaps more intriguingly, whales are also a case study in the gradual evolution of mammals from fully terrestrial to fully marine lifestyles, with corresponding adaptations (elongated bodies, webbed feet, blowholes, etc.) at various key intervals along the way. Until the turn of the 21st century, the ultimate origin of whales was shrouded in mystery, with scarce remains of early species. That all changed with the discovery of a huge trove of fossils in central Asia (specifically, the country of Pakistan), some of which are still being analyzed and described. These fossils, which date from only 15 to 20 million years after the demise of the dinosaurs 65 million years ago, prove that the ultimate ancestors of whales were closely related to artiodactyls, the even-toed, hooved mammals represented today by pigs and sheep. The First Whales - Pakicetus, Ambulocetus, and Rodhocetus In most ways, Pakicetus (Greek for Pakistan whale) was indistinguishable from other small mammals of the early Eocene epoch: about 50 pounds or so, with long, dog-like legs, a long tail, and a narrow snout. Crucially, though, the anatomy of this mammals inner ears closely matches that of modern whales, the main diagnostic feature that places Pakicetus at the root of whale evolution. One of Pakicetus closest relatives was Indohyus (Indian pig), an ancient artiodactyl with some intriguing marine adaptations, such as a thick, hippopotamus-like hide. Ambulocetus, aka the walking whale, flourished a few million years after Pakicetus and already displayed some distinctly whale-like characteristics. Whereas Pakicetus led a mostly terrestrial lifestyle, occasionally dipping into lakes or rivers to find food, Ambulocetus possessed a long, slender, otter-like body, with webbed, padded feet and a narrow, crocodile-like snout. Ambulocetus was much bigger than Pakicetusabout 10 feet long and 500 pounds, much closer to a blue whale than a guppyand probably spent a significant amount of time in the water. Named after the region of Pakistan where its bones were discovered, Rodhocetus shows even more striking adaptations to an aquatic lifestyle. This prehistoric whale was genuinely amphibious, crawling up onto dry land only to forage for food and (possibly) give birth. In evolutionary terms, though, the most telling feature of Rodhocetus was the structure of its hip bones, which werent fused to its backbone and thus provided it greater flexibility when swimming. The Next Whales - Protocetus, Maiacetus, and Zygorhiza The remains of Rodhocetus and its predecessors have been found mostly in central Asia, but the larger prehistoric whales of the late Eocene epoch (which were able to swim faster and farther) have been unearthed in more diverse locations. The deceptively named Protocetus (it wasnt really the first whale) had a long, seal-like body, powerful legs for propelling itself through the water, and nostrils that had already begun to migrate halfway up it foreheada development foreshadowing the blowholes of modern whales. Protocetus shared one important characteristic with two roughly contemporary prehistoric whales, Maiacetus, and Zygorhiza. The front limbs of Zygorhiza were hinged at the elbows, a strong clue that it crawled onto land to give birth, and a specimen of Maiacetus (meaning good mother whale) has been found with a fossilized embryo inside, positioned in the birth canal for terrestrial delivery. Clearly, the prehistoric whales of the Eocene epoch had a lot in common with modern giant tortoises! The Giant Prehistoric Whales By about 35 million years ago, some prehistoric whales had attained gigantic sizes, bigger even than modern blue or sperm whales. The largest genus yet known is Basilosaurus, the bones of which (discovered in the mid-19th century) were once thought to belong to a dinosaurhence its deceptive name, meaning king lizard. Despite its 100-ton size, Basilosaurus possessed a relatively small brain and didnt use echolocation when swimming. Even more important from an evolutionary perspective, Basilosaurus led a fully aquatic lifestyle, birthing as well as swimming and feeding in the ocean. Contemporaries of Basilosaurus were much less fearsome, perhaps because there was only room for one giant mammalian predator in the undersea food chain. Dorudon was once thought to be a baby Basilosaurus; only later was it realized that this small whale (only about 16 feet long and half a ton) merited its own genus. And the much later Aetiocetus (which lived about 25 million years ago), though it weighed only a few tons, shows the first primitive adaptation to plankton feedingsmall plates of baleen alongside its ordinary teeth. No discussion of prehistoric whales would be complete without a mention of a fairly new genus, the aptly named Leviathan, which was announced to the world in the summer of 2010. This 50-foot-long sperm whale weighed only about 25 tons, but it seems to have preyed on its fellow whales along with prehistoric fish and squids, and it may have been preyed on in turn by the largest prehistoric shark of all time, the Basilosaurus-sized Megalodon.

Signs youre stuck in the rat race

Signs youre stuck in the rat race We’ve all heard the phrase rat race before- it refers to a seemingly never-ending, pointless, and even self-defeating pursuit, and it’s often used when referring to one’s job or career. Individuals who are stuck in the rat race are unhappily going through the motions in life, trudging through the daily grind of their workday feeling unfulfilled, unchallenged, and uninspired until they go home at the end of the day- only to repeat the whole process again. Individuals who are stuck in the rat race are more than just unhappy- they’re actually negatively affecting their health and well-being. According to a recent Forbes article, individuals who hate their jobs face some serious consequences, including increased risks for stress, sleeplessness, illness, and mental health issues. An article by The Atlantic  even goes on to suggest that workplace unhappiness can shorten your lifespan!Obviously, individuals who are stuck in this unfortunate situation have every good reason to try and get out of it. Are you one of them? The truth is, sometimes people get so busy and wrapped up in the responsibilities and activities they have going on in their daily lives that they fail to take stock of their current situations. You may very well be stuck in the rat race and not even know it!Use the following signs to determine if you need to make some changes to your daily life.1. Your energy and enthusiasm levels are low.Are you like the energizer bunny when you get up in the morning? Do you go through an average workday full of â€Å"get up and go† enthusiasm for what lies ahead? Or maybe you’re more like a wilted flower or droopy basset hound who practically needs to be dragged through the day, and can’t wait to get back home so you can†¦lie around and do absolutely nothing. We all have good days and bad, but if more often than not you’re facing each day with a real lack of energy and enthusiasm, that’s a good sig n your stuck in a rat race and may need a change.2. You’re stuck in the past.Do you spend more time thinking about â€Å"past glories† than future opportunities? Do you gladly reminisce about days gone by and what you have done at the expense of what lies ahead and what you will accomplish? Individuals who are stuck in the rat race avoid thinking about the present and the future as a protective mechanism- keeping them from having to confront an unhappy reality or an uncertain tomorrow. If this sounds like you, you might just be stuck in a rut.3. You lack purpose.Folks who are in happy places in their lives are fueled by a sense of purpose and gamely tackle each day, along with the challenges and goals they’ve set for themselves. Those stuck in less fulfilling situations? Not so much. And it’s not hard to imagine the vicious spiral this creates, leading you to accomplish less and less as the days drag on. Don’t get stuck in a rat race spiral!4. Youà ¢â‚¬â„¢re noticing changes in your health and wellness.We’ve already touched on this one- when you’re stuck in the grinding gears of the rat race you’re going to experience a negative effect on your health and well-being. The ravages of stress, tension, sleeplessness, anxiety, and more will begin to gnaw away at you- and you’ll notice it. Tack on to this that people stuck in the rat race often make poor diet and exercise choices and it’s easy to see that this is a road to ruin.5. You feel powerless to effect change or think there’s nothing better out there for you.One of the real tragedies of being stuck in the rat race- as if we haven’t mentioned enough of them already- is that it robs you of the very ability to see a way out of it. It’s common for those stuck in a rut to feel that there’s simply no way out or have such a negative raincloud following them that they can’t even fathom that there’s something better out there. It’s not a good place to be.If after reading this you’ve realized that you’re stuck in the rat race and are starting to worry or panic- take a deep breath. It’s always better to know the truth and it’s never too late or a bad time to figure out where you are with your job situation- good or bad- and make a change!