Reconstruction of Pakicetus attocki (fossil whale) by James St. John: www.flickr.com
In Judaism, we have a mechanism for connecting the dots or filling in the gaps where the Biblical text seems to require it. This mechanism is called “Midrash”. In terms of providing understanding, these Midrashim written by our Sages, some more than 2000 years ago, are extremely beneficial.
When modern scientists want to flesh out the theory of evolution, they have come up with their own brand of “Midrashim”.
This is one of their tales, mostly fact, perhaps part fiction and definitely part speculation. It is the story of the whale, a creature whose forbearers emerged from the sea, then inhabited dry land and subsequently returned to the oceans where they originally started out from…all this taking place over the course of some 350 million years of Earth’s history.
All life on Earth began in the sea about 3.8 billion years ago. Except for plants, the early continents were completely barren of life forms when they first emerged from the sea. Then, 419 million years ago some crustaceans (the crabs) and their relatives left the sea and began inhabiting the land.
These were gradually followed by a host of vertebrate life forms. Because they walked on four legs, they are called “tetrapods”. In a span of just 20 million years after leaving the sea they achieved a fully terrestrial lifestyle.
Most vertebrate land animals that we know today, even human beings who walk on two legs, are called tetrapods. I guess they came ashore to escape predation or because there were better things to eat on land. You can view it as a Prehistoric Exile for marine animals, a major dispersion to the Galut.
For an aquatic animal to be able to venture onto land and live on land, several important modifications must take place in its body physiology. In order to cope with the new environment, it must be able to breathe atmospheric air instead of breathing with gills like fish.
Its skeleton needed to be strengthened in order to support the weight of the animal on land. And these creatures initially had to live near water so that their skin and eggs would not dry out.
A solution to the drying out problem was the evolution of waterproof skin that could prevent the animal from drying out, and the evolution of a watertight membrane, called the amnion, surrounding their eggs.
These tetrapods are called amniotes and through subsequent geological time, amniote vertebrates successfully diversified and adapted to a life in virtually all the ecological niches on land. We humans are amniotes.
Fast forward to about 50-60 million years ago. The dinosaurs have gone, wiped out by the impact of a large asteroid. Mammals are on the rise, and the common ancestor to both the modern-day hippopotamus and whale is alive and kicking. Who this creature was is a matter of speculation.
Just because you are a professor and wear a white lab coat doesn’t mean you know everything. But in regard to the first whale, scientists do have an opinion, and a good one at that.
The fossil records for whales and their intermediate or transitional forms are pretty extensive. A terrestrial tetrapod called Pakicetus may be the earliest whale precursor. The Pakicetus was a typical land animal. It had a long skull and large carnivorous teeth, a distinct and flexible neck and a very long and robust tail.
As in most land mammals, the nose was situated at the tip of the snout. It was the size of a small wolf.
From the outside, they don't look like whales at all. However, their skulls – particularly in the ear region, which is surrounded by a bony wall – strongly resemble those of living whales and are unlike those of any other mammal.
A question arises as to why the Pakicetus wanted to leave the land and return to the sea?
I see most things through the lens of Torah. I imagine Pakicetus and its precursor, whatever that was, petitioning Hashem to return it to its ancestral home, an ingathering of sorts, a “prehistoric oceanic Zionism”. And Hashem in His mercy granted the request, but cautioned Pakicetus and its precursor that there would be a journey, and not one of 40-year duration, but of eons, because there was a lot of work to be done.
The closest living relative to a whale is the hippopotamus. Whatever it was, the hippo and the whale evolved from a common ancestor.
In a similar fashion, our closest living relative is the chimpanzee, and humans and Bonzo the ape also evolved from a common ancestor.
This means that, my ex-mother-in-law aside, humans did not come from monkeys, but each struck out on individual paths from a common relative, whose identity is another matter of speculation. What chimps are to humans, hippos are to whales.
Getting back to the whale, it had to undergo a complete makeover, a change in life style, in order to go from being a land creature to becoming a denizen of the deep. It did this over a period of about 20 million years, starting 50 million years ago. There were many hurdles to overcome. Some call these hurdles the “Aquatic Problem.”
In terms of design modifications, these are some of the environmental circumstances that Hashem had to consider:
On land, the tetrapod whale ancestor used its feet to push against the ground in order to move forward, but in an open ocean it had to swim. This means it had to develop adaptations that allowed it to push against the water in order to move.
Almost all aquatic amniotes have developed flippers, which are limbs adapted to steer and to generate thrust in water, similar to paddles.
The tetrapod whale ancestor needed to develop a type of movement called “axial locomotion”. This is when an animal generates thrust with its head, spine, and tail, which undulate continuously as they swim.
In order to generate more thrust from its tail, a precursor to the whale increased the surface area of its tail and in particular the end of its tail, making it a fast swimmer.
Terrestrial animals only move in two dimensions, but aquatic animals move in three and this means that aquatic animals have to be stable in three dimensions, instead of just two.
A fully aquatic animal needs to be able to control its up-down, left-right motions, and also needs to be able to control how much it rolls.
Whales use their flippers for maneuvering and stabilizing their body so they don’t roll sideways while moving forward. Some whales have a prominent dorsal fin, which helps stabilize the body against rolling, especially those that typically move at great speeds.
The high density of water as opposed to air causes a problem called “drag”. In order to overcome drag, you need a streamlined body that is elongated and smooth, nothing like a hippopotamus. And a whale is much more streamlined.
How does a whale get its drinking water? The simple answer is that we really do not know. The best guess is that when whales take in salt water, their kidneys are able to separate out salt from seawater and other fluids, and the salt is flushed out in very salty urine.
A big challenge is buoyancy. If you are aquatic, you have to be buoyancy neutral. The problem is lungs. Whales did not give up their lungs in return for gills. I don’t know why. Having lungs is like having bags filled with air, and they make you positively buoyant, propelling you to the surface.
Scuba divers attach weights around their middle to counter this effect. Whales increase the density of their bones in order to achieve neutral buoyancy.
A whale has a blowhole at the top of its head through which it breathes air when the whale surfaces. This is very different from Pakicetus, whose nose was located at the tip of its snout.
When whales dive under water, they have a nasal plug that covers the nasal passage to the blowhole and keeps water from entering their lungs.
The ocean depths are cold. Whales do not have the luxury of a wet suit, but they have put on an insulating layer of fat called blubber that keeps them warm.
The ocean depths are also dark; it is difficult to see, so the whale’s eyes had to be enlarged, and a greater emphasis was put on hearing rather than seeing as a means of finding food and avoiding predators.
Whales do have ears, but the external formation of an ear is gone, and the bones of the middle ear are enlarged, making their hearing more acute. Just think of Pakicetus and its specialized ear.
Again, looking at the evolution of whales through the lens of Torah, it is obvious that transitioning from a terrestrial life to a marine life did not happen overnight.
In my mind’s eye, regarding the journey embarked upon by Pakicetus, there may have existed up in heaven something tantamount to Israel’s Law of Return, and in making aliyah, old Pakicetus was only exercising his God-given right.
■Michael Jaron lives in Nahariya. He is a co-founder of the ESRA’s North Coast branch and is a volunteer tutor.