Last of the giant tuskers
QUESTION Are some elephants evolving without tusks?
The reduction in the size of elephants’ tusks — even their disappearance — has been observed for at least 150 years.
It has been touted as ‘evolution happening before our eyes’ by controversial biologist Richard Dawkins, but in fact it is no such thing.
The cause is an artificial natural selection caused by poaching of ‘giant tuskers’. elephants with larger tusks, which are in possession of the genes that make larger tusks, are preferentially hunted. This removes them from the gene pool.
elephants with small-tusk genes are left to reproduce, meaning subsequent generations have smaller tusks. Those with defective genes that fail to grow tusks at all are similarly favoured. But no genetic information has been added in either case.
Darwinian ‘pond scum to Man’ evolution requires the addition of new and highly complex genetic information. What is happening with the elephants is a loss of genetic information.
Chris Stradling, Meols, Wirral.
QUESTION Would a car fuel tank explode if hit by a bullet?
The short answer to this question is no, but the explanation as to why comes in several parts.
Anyone who has poured cold brandy onto a Christmas pudding and then tried to light it will know how hard that is to do. however, if you heat the brandy first, it will light easily. This is because it isn’t the brandy that burns, it is the vapour from the brandy, which is released when it is heated.
The same applies to petrol, diesel and aviation fuel. For a petrol or diesel explosion to take place, it requires fuel (vapour), oxygen (air) and an ignition source (a spark, flame or high temperature). If any of these three are missing, then the explosion won’t take place.
In the case of a fired bullet, it is the heat source that is missing, because bullets don’t get hot enough to cause ignition.
You can drop a lit match into a pool of petrol and it will just fizzle out. however, hold the same lit match half an inch above the pool, where the vapour combines with air to form an explosive mixture, and it will explode.
If a bullet punctures a fuel tank, it will be immersed in liquid fuel, not vapour, and therefore the fuel can’t explode.
If the fuel vapour is hot enough, it will reach what is known as its autoignition temperature and explode spontaneously. For petrol vapour, this temperature is 280c and for diesel it is 256c.
Bob Cubitt, Northampton.
QUESTION Should the U.S. be more worried about the Cascadia Fault than the San Andreas Fault?
The San Andreas Fault, which runs nearly the length of California, was the site of a devastating earthquake in 1906 that wiped out 80 per cent of the city.
Its infamy and location have made it one of the most studied fault lines in the world. however, seismologists believe the upper limit of an earthquake here is between 8.2 and 8.3 on the Richter scale — a powerful quake, but, because the Richter scale is logarithmic, only 1/20th as strong as the 2011 megathrust earthquake in Japan, which measured 9.1 on the Richter scale and triggered the tsunami that killed 22,000 people and destroyed the Fukushima nuclear plant.
Just north of the San Andreas, however, lies the Cascadia Subduction Zone (CSZ). A subduction zone is a region of the planet where one tectonic plate is sliding underneath another. Tectonic plates are those slabs of mantle and crust that, in their epochs-long drift, rearrange the earth’s continents and oceans.
The CSZ is a 620-mile-long dipping fault that stretches from Northern Vancouver Island to Cape Mendocino, California.
It separates the Juan de Fuca and North American plates. The new Juan de Fuca plate (once part of a much larger oceanic plate) has been created offshore along the Juan de Fuca ridge. This is moving towards, and will eventually be shoved beneath, the North American plate.
Under pressure from Juan de Fuca, the stuck edge of North America is bulging upwards and compressing eastward, at the rate of, respectively, 3mm to 4mm and 30 mm to 40 mm a year.
The centre of the continent is a giant stable mass called the craton against which the plate will rebound like a spring. If, on that occasion, only the southern part of the Cascadia subduction zone gives way, the magnitude of the resulting quake will be between 8.0 and 8.6.
If the entire zone gives way, an event that seismologists call a full-margin rupture with the fault in a megathrust earthquake, the magnitude will be somewhere between 8.7 and 9.2 on the Richter scale — a huge quake on a par with the Japanese event.
Dr Ken Warren, Glasgow.
QUESTION Was General Robert E. Lee a Democrat?
FURTHER to the earlier answer, Robert e. Lee was certainly a Democrat (the party was pro-slavery in the South and anti-slavery in the North), but before the outbreak of civil war in 1856 he described slavery as a ‘moral and political evil’ and also spoke against secession.
he was offered overall command of the Union Forces by General Winfield Scott.
When Virginia — his home state — joined the Confederacy, he said: ‘I cannot raise my hand against my birthplace, my home, my children’ and accepted command of the Virginia militia. his reward was to see his home at Arlington later converted into a national cemetery.
Patrick Hayward, St Albans, Herts.