This is called an endoptic phenomenon.  The eye has amongst the highest metabolic rate for any tissue in the body, higher even than most brain tissue.  That’s because the retina is incredibly energy hungry, when light shines into the eye, it actually switches retinal activity off, so in the dark your eye is even more active than it is in the light!

When you, for example, stand up from a hot bath, the momentary dip in blood pressure causes you to see funny lights because the blood supplying the retina temporarily drops in flow and reduces the oxygen and sugar available to the retina.

The eye is full of fluid and jelly called aqueous humour, so when you press on it the pressure gets transferred straight to the back of the eye, squashes the blood vessels a bit and changes the pressure.  This reduces profusion, it stops blood going in so easily.

Secondly, the physical distortion of the retina itself can cause some photoreceptors to change shape and become less active, firing off impulses when they shouldn’t be.  This causes internally generated endoptic phenomena.

The Blue Whale is the loudest animal in the world and it makes a sound up to about 188dB.  For comparison, a jet engine at take off is about 140 dB, and the human pain threshold is about 120dB.  Humpback Whales are not as loud, but they’re more like the Mariah Carey of the whale world as they have really complex whale songs with a really wide frequency range.

The amplitude of whale song is measured underwater, so although it would be painful to humans, it doesn’t hurt other animals in the sea because they have different ears and can tolerate such high amplitudes.

There is a very famous dog, a Border Collie, called Rico who has been written about in the journal "Science" as having a registered vocabulary of 240 words.  Rico’s owners demonstrated that he has the equivalent learning abilities of a human toddler by showing context-specific learning and attribution. 

By putting Rico in one room and a number of his toys in another room, and then asking him to retrieve one by name, he would get the right toy.  He was then told to go and fetch an item he had never seen or heard of before. This object was placed amongst a collection of toys he knew in the other room. By a process of elimination he was able to pick this object as it was the single item for which he did not know the name. He correctly inferred, therefore, that this must be the item to which his owner was referring. Humans learn by the same deductive process.

So yes, dogs can have a vocabulary and therefore can understand some language and probably use a similar region of their brain to that which we use for language.

The only reason we look different is due to genetic segregation, people weren’t hugely mobile historically and they adapted to suit their environment. People in Africa are usually subject to more sun and ultra violet (UV) radiation and so they developed heavily melanised, brown skin to combat the UV. As people migrated north away from Africa, they were exposed to less UV radiation and it became energetically costly to put all that energy in to making our skin brown when we didn’t really need it, so it didn’t matter if skin was a little paler.

With the mobile populations we have today, there’s a chance that we might see ourselves turning into a more homogeneous mix again.

You can freeze all sorts of things, sperm, eggs, embryos… They aren’t just frozen in water, they are mixed with a chemical such as dimethyl sulphoxide, which alters the freezing properties of the water in the cells and acts an antifreeze. This stops the water making large crystals and damaging the cells.