The Kabwe skull (Homo rhodesiensis)

The Kabwe skull or Broken Hill 1 is a hominin fossil originally classified as Homo rhodesiensis. It was found in an iron and zinc mine in Broken Hill, Northern Rhodesia (now Kabwe, Zambia) in 1921 by a Swiss miner named Tom Zwiglaar. In addition to the skull, several postcranial bones were found including a femur and a tibia. The skull became known to anthropologists as Rhodesian Man but is now commonly referred to as the Broken Hill or Kabwe skull. The Kabwe skull is estimated to have a cranial capacity of 1,100cc. It has heavy brow ridges and a slightly keeled and constricted frontal bone.

The age of the remains are contentious, with secure dating impossible due to the destruction of geological context by mining activity. Archaic mammal species recovered with the skull suggest a date of 700,000-400,000 years old (Scarre, 2005). Conroy (1997) cites archaeological and palaeontological evidence that give a date of more than 125,000 years; Lewin & Foley (2004) give an age of “at least 200,000 years”.

The Kabwe skull was until recently classed as “archaic Homo sapiens” but is usually now classed as Homo heidelbergensis. Some authorities retain the H. rhodesiensis classification and reserve H. heidelbergensis for European hominins.


Conroy G (1997): “Reconstructing Human Origins: A Modern Synthesis”, W.W. Norton & Co. Inc, New York, NY & London.

Lewin, R and Foley, R 2004: Principles of Human Evolution (2nd edition), Blackwell Science Ltd.

Scarre C (2005) (Ed): “The human past”, Thames & Hudson.

© Christopher Seddon 2008


Ice Ages

Introduction: We live in an era where even politicians have realised the significant threat climate change poses to civilization and indeed to all life on Earth, but it is nothing new and has been a major driving force of evolutionary change for hundreds of millions of years. One species that undoubtedly owes its very existence to climate change is Homo sapiens. It is no coincidence that the earliest human species, Homo habilis, emerged at just about the same time as Earth entered an ice age. The subsequent epochs of advancing and retreating ice sheets have played a pivotal role in the evolution and dispersal of subsequent human species, culminating in that of modern humans, Homo sapiens.

The Current Ice Age: We now know that the Earth has been affected by a number of ice ages in its history. The current Ice Age begun 2.6 million years ago and has been characterised by the advance and retreat of major glaciers and ice sheets in glacial periods punctuated by warmer interglacial periods. The last glacial period – or what is popularly known as the last Ice Age – began 110,000 years ago and ended with the onset of the Holocene epoch 11,600 years ago. The Ice Age is not in fact at an end and barring the effects of global warming, the glaciers and ice sheets will one day return.

The origins of the current Ice Age go back some 50 million years. Throughout this time the Earth’s climate has been cooling. Though the reasons are not fully understood, the collision of India with the Eurasian landmass (48-52 million years ago) and the migration of Antarctica to the South Pole (23 million years ago) are thought to be factors. From the first of these two events arose the mountains of the Himalaya Range, uplifted by the collision. The weathering of this new mountain range sequestered CO2 from the atmosphere, leading to global cooling. Subsequently the presence of a large landmass at the South Pole encouraged the build-up of ice. These ice-sheets reflected more of the Sun’s radiation back into space leading, in turn, to further cooling. The tipping point was reached 2.6 million years ago, with the expansion of ice sheets in the Northern Hemisphere.

Discovery: Perhaps surprisingly, the discovery that the northern glaciers had once been far more extensive, reaching as far south as London, New York and Berlin, is comparatively recent. Not until the 19th Century did geologists began to ponder such anomalies as bones of reindeer in the south of France and granite boulders high up on the slopes of the predominantly limestone Jura Mountains. The German-Swiss geologist Jean de Charpentier suspected that the boulders might have been deposited there by glaciers. He discussed the idea with his friend and fellow geologist Louis Agassiz, who took it up with great enthusiasm.

Meanwhile the naturalist Karl Friedrich Schimper, who was also a friend of Agassiz, was also of the opinion that ice sheets had once been far more extensive than now, and had once lain across much of Eurasia and North America. But he was a man who very rarely put his ideas into writing. He did however lend Agassiz his notes, but to his and de Charpentier’s considerable annoyance Agassiz subsequently took all the credit for the theory, which he put forward in a two-volume work entitled Etudes sur les glaciers (Study on Glaciers), published in 1840.

The main problem with the theory as it stood was that it offered no explanation for the cycles between glacial and interglacial periods. That these might have an astronomical cause was first suggested by Scottish scientist James Croll in 1860, who claimed that cyclical changes in the Earth’s orbit around the Sun might be responsible. Croll’s theory attracted considerable interest at the time, but had been more or less abandoned by the end of the 19th Century. The theory was revived and extended in the 1920s and 1930s by a Serbian engineer named Milutin Milanković.

The Milanković Pacemaker: The Earth’s seasons arise from its axis of spin being tilted rather than upright in relation to the plane of its orbit. When either the Northern or the Southern Hemisphere is tilted towards the Sun, it will experience summer as a result of both longer hours of daylight and the Sun being higher in the sky and more of its heat reaching the ground. The other hemisphere, meanwhile, will experience winter. For the Northern Hemisphere, the day with the longest period of daylight or Summer Solstice occurs on 21 June. The day with the shortest period of daylight or Winter Solstice occurs on 21 December. The spring and autumn equinoxes occur when the Earth is mid-way between the solstice positions, and everywhere receives 12 hours of daylight.

At the present time in the Northern Hemisphere, summers are hot enough to melt the whole of the previous winter’s accumulation of snow, but if this was not the case then the latter would gradually build up and ice sheets would advance into temperate latitudes. The enlarged ice sheets would then reflect more of the Sun’s radiation straight back into space, causing the cooling process to accelerate.

Milanković considered the possible effects of astronomical cycles on the intensity of the seasons, the amount of sunlight received (“insolation”) in the Northern Hemisphere and the possibility that at certain times the summers in the Northern Hemisphere might not be hot enough to prevent ice sheets from building up. He took into account three variables now known as the Milanković Cycles: precession of the equinoxes; variation of the axial tilt (“obliquity”) and changes in the shape of the Earth’s orbit around the Sun (“eccentricity”).

Precession is the long-term oscillation experienced by the Earth in which the spatial orientation of the axis changes with time. The phenomenon may be likened to the wobbling of a spinning-top or a gyroscope and is caused by caused by tidal effects of the Moon and Sun. A complete cycle takes 25,800 years. Precession affects the time of the year when the Earth is at is closest to the Sun (“perihelion”), which in turn will affect the intensity of the seasons. The picture is complicated by the precession of the orbit itself, with the perihelion slowly migrating around the Sun in a 105,000 year cycle. If these are combined with cyclical changes in the shape of the Earth’s orbit, a periodicity of 21,700 years is obtained for perihelion coinciding with summer in each hemisphere.

The Earth’s axial tilt is currently 23.5 degrees, but varies between 21.8 and 24.4 degrees over a period of 41,000 years. The seasons for both hemispheres will be exaggerated when the angle of tilt is high and moderated when it is low.

Finally the Earth’s orbit changes from near-circular (“low eccentricity”) to an ellipse (“high eccentricity”) with a major cycle of 400,000 years and a number of smaller cycles that average out at 100,000 years. At times of high eccentricity, the seasons are exaggerated in the hemisphere experiencing summer close to perihelion, and moderated in the other.

How these differing cycles combine to either exaggerate or moderate the seasons is of course very complicated, and Milanković spent many years laboriously performing the relevant calculations which – in an era before computers – all had to be carried out with the aid of a slide rule and books of tables. Unfortunately his dates for glacial periods did not tally with the then accepted values, and his theory fell out of favour. However in the late 1960s and early 1970s advances in methods for dating proxy evidence (indications of glacial periods) vindicated Milanković’s predictions and his theory gained widespread acceptance.

Although the duration of glacial periods is now seen to correspond closely to expectations, different cycles seem to have dominated at different times. Prior to 800,000 years ago, glacial periods followed the 41,000 year obliquity cycle, but subsequently the 100,000 year orbital eccentricity cycle has been dominant.

Effect upon Sea Levels: During glacial periods, significant amounts of water are locked up in ice sheets and sea levels fall. At the time of the Last Glacial Maximum (LGM), when the ice sheets reached their maximum extent, 20,000 years ago, sea levels were roughly 120 metres below their present-day level. Britain and Ireland were joined to continental Europe and the Indonesian islands as far east as Borneo and Bali were joined to mainland Asia as part of a subcontinental landmass known as Sundaland. Australia was connected to New Guinea and Tasmania and though it remained separate from Sundaland, the gap was small and could be crossed by humans living at that time.

Effect upon Climate: During the LGM, the climate throughout the world was cooler and dryer. The arid conditions were a consequence of so much water being locked up in ice sheets. In some parts of the world such as Southern Australia and the Sahel Belt south of the Sahara, rainfall dropped by up to 90 percent. Throughout the world deserts expanded and rainforest shrank.

During interglacial periods, the climate is warmer and wetter. In Africa, a weather phenomenon known as in Inter-Tropical Convergence Zone (ITCZ), which normally brings monsoons to the tropics, can extend its influence northwards. During such epochs, the Sahara experiences moist wet conditions and savannah climate. The last such climatic optimum was the Holocene Thermal Optimum, which began at the end of the last glacial period and peaked around 4000 BC. Subsequently, Milanković-determined insolation declined, the ITCZ returned southwards and the Sahara rapidly dried up.


Bryson, B. (2003) A Short History of Nearly Everything, Doubleday.
Evans, E.P. (1887) The North American review, Volume 145, Issue 368, July 1887.
Klein, R. (1999) The Human Career (2nd Edition), University of Chicago Press.
Wilson, R.C.L., Drury S.A. and Chapman J.L. (2000) The Great Ice Age, Routledge.

© Christopher Seddon 2008

The Star

Attempts to seek an astronomical explanation for the Star of Bethlehem are in my view misguided. Relatively common events such as planetary conjunctions, comets or bright meteors would not have persuaded three wise men worthy of the name to stock up on gold, frankincense and myrrh and head west to Bethlehem in search of the Messiah, dropping in on King Herod en route. The people of the East were sophisticated astronomers who had in all probability been studying the heavens since prehistoric times, and they would have been aware that these things were nothing out of the ordinary.

More feasible is the idea that they saw a supernova – an event of the type that might only happen every few centuries. This idea formed the basis of Sir Arthur C. Clarke’s classic short story The Star, about a Catholic priest who queried his faith when he realised the explosion had wiped out an alien civilization. More recently, American cosmologist Frank Tipler has suggested that a Type 1C hypernova – a stupendously powerful supernova – in the Andromeda Galaxy was what the Magi might have seen.

But even the supernova theory has one fatal flaw. The world at around 4 BC – the presumptive birth date of Christ – lay well within the realms of recorded history, and a supernova had it occurred would have been widely noted and recorded. But the Star of Bethlehem is attested only once, in the Gospel according to St Matthew (Matt 2: 1-12), which is believed to have actually been written by an anonymous Christian decades after the events it describes.

It is far more likely that that the reference to a star is no more than a metaphor, rather like the present-day usage of the word to describe notable actors, footballers, musicians, etc and that the “star” of Bethlehem is simply an allusion to Jesus rather than an astronomical phenomenon.

© Christopher Seddon 2008

Colour-change Paperweight

Alexandrite is an extremely rare gemstone with the property to change from purple to green. It appears purple under artificial light and green when viewed in daylight. The gemstone is named for Tsar Alexander II of Russia, on whose 16th birthday it was discovered, and fine examples can cost up to $100,000 per carat. I was quite astonished to discover that a rather less expensive Caithness glass paperweight in my possession for the last twenty years can do more or less the same thing! In daylight, or under normal incandescent or halogen lighting it appears a rich purple:

But I recently installed compact flourescent lighting, and under this the paperweight turns blue:

The likely explanation for this phenomenon is that the purple-coloured glass contains a mixture of red and blue colourants. Under daylight or a continuous-spectrum artificial light, these appear purple. However flourescent lighting is deficiant in red wavelengths and when illuminated by such lighting, the red colourants are not seen, causing the paperweight to appear blue.

© Christopher Seddon 2008

Aboriginal Australian Art on Coins

Modern humans are believed to have reached Australia from 40,000 to 50,000 years ago (e.g. Scarre, 2005; Wade, 2007) and possibly even earlier (e.g. Wells, 2002; Oppenheimer, 2003). There is little doubt that these first Australians possessed the capacity for art and were in all probability producing artwork at the same time as their European counterparts were adorning the Chauvet Cave in France, but the earliest known Aboriginal Australian rock art dates from 20,000-30,000 years ago (Scarre, 2005). It is possible that works predating these were located in coastal regions that were inundated when sea-levels rose at the end of the last Ice Age, as indeed happened in Europe where some cave art, such as that at Cosquer Cave near Marseille, can now only be accessed by scuba divers.

Today, Aboriginal Australian art is widely admired and, inevitably, it has featured periodically on Australian coinage. The Royal Australian Mint in Canberra is one of two mints operating in Australia and some of its numismatic offerings are produced in direct competition to those from its older counterpart, the Perth Mint. One of the most appealing coins it has produced is the Kangaroo, a one ounce silver bullion coin with a face value of Aus $1, featuring a changing design based on the marsupial mammal that has become virtually synonymous with Australia. Different artists are featured each year, but the most vibrant designs so far seen were those of the mini-series by Aboriginal Australian artists that ran between 2001 and 2003.

The 2001 design was by Jeanette Timberly, of the Bidjigal Tribe. She was born in La Perouse, NSW.

The 2002 design was by Mark Nodea of the Gija Tribe in Eastern Kimberley, WA. He was born in Derby, WA in 1968. He currently resides in Kununurra and is former Chairperson of the Warmun Art Centre. Mark is a Traditional ochre artist but he works in other media and is also noted for his charcoal sketches and figurative acrylic works.

The 2003 design was by Ray Thomas of the Gunnai people of Victoria. He was born in Melbourne in 1960. See his personal website.

© Christopher Seddon 2008


First broadcast on 19 January 1967, the Star Trek episode Arena is generally regarded as being one of the most memorable episodes from the Original series. The screenplay was written by Gene L. Coon and officially it is based on a short story of the same name by Fredric Brown, first published in the June 1944 issue of Astounding magazine. Brown receives a story credit at the end of the episode. However it has been claimed that the similarity between the short story and Coon’s screenplay was only noticed after the latter had been written and that Brown was totally unaware of this when he agreed a fee for the use of his work!

In the Star Trek episode, the USS Enterprise goes in pursuit of a Gorn warship which has made a seemingly unprovoked attack on the Federation outpost on Cestus III, but as the chase leads into an unexplored sector of space, both ships are brought to a grinding halt by omnipotent beings calling themselves the Metrons. Kirk is informed that he will be teleported to a life-sustaining planet together with the captain of the Gorn ship. He will have no weapons or means of contacting the Enterprise and he must fight the Gorn to the death. The winner and his ship will be allowed to go free, but the loser will be destroyed, together with his ship. He will be provided with a recording device and the planet will contain the resources needed to make weapons.

Without any further ado, Kirk finds himself facing the Gorn on the hot, arid surface of an unknown planet (actually Vasquez Rocks, California). The Gorn is a huge, reptilian being and it soon becomes clear that Kirk is no match for him. Kirk hurls a rock at the Gorn, who merely hurls a much larger one back. Kirk then rolls a huge boulder on top of the Gorn. This which seems to have done the trick – but the Gorn revives and pushes the boulder aside. Kirk runs, but falling into a snare set for him by the Gorn. He manages to escape, but is injured in the process. By now he is tiring and the Gorn – by means of the recording device which is also a two-way radio – appeals to him to give up and promises to kill him quickly. Kirk also learns that the Cestus III outpost had been set up in Gorn territory, and the attack was made because the Gorn feared it was the precursor to an all-out invasion.

But Kirk then realises that there are indeed enough natural resources on the planet to make a weapon. Using sulphur, coal and saltpetre he makes gunpowder; this he loads into a gun barrel made from a bamboo-like plant together with some extremely large diamonds – “the hardest material in the universe”.

Kirk manages to disable the Gorn with this crude weapon, but he then refuses to kill his enemy. The Metrons are impressed by this “advanced trait” of mercy and allow both ships to go on their way.

Possibly because they weren’t bad guys after all, the Gorn never again made a major appearance in any Star Trek series. But if the Gorn were never seen again, the plot-line to Arena most definitely was.

It appeared in a second-season episode of Space 1999 entitled The Rules of Luton, set on an alien planet called Luton. You are reading this correctly. There really was an episode of Space 1999 set on a planet called Luton, albeit pronounced with the stress on the second syllable.

Plants are the dominant form of life on Luton, and when Koenig and Maya are dropped off by Verdecci in an Eagle spacecraft and begin helping themselves to some tempting-looking berries, the locals aren’t amused. They are ordered to fight a group of three alien trespassers to the death. Maya’s shape-shifting abilities prove to be a two-edged sword. She turns into a lion, startling one alien to the extent that it falls into a river and drowns. A second alien is soon dealt with but after Maya turns into a hawk in order to carry out some aerial reconnaisance, she is captured by the remaining alien and shut up in a birdcage.

She can only hold her form for an hour, at the end of which she will return to human form and be crushed to death. Why she doesn’t simply escape by turning into an insect (as she did in a later episode) isn’t made clear. How Maya can turn into creatures of such varying sizes and of course masses also remains unclear, but as noted in an earlier entry the screen writers of Space 1999 never let the laws of physics get in the way of a good story, much less a crap one like this. Inevitably Koenig rescues Maya and soon has the remaining alien at his mercy, refuses to kill him, and is allowed to go free by the Judges of Luton.

The writers of Blake’s Seven obviously believed they could improve on this lacklustre offering and came up with Duel, a title that at least subtly acknowledges the story’s origin. In this incarnation, the Liberator is recharging its batteries when it is attacked by a battlegroup of Federation pursuit ships, with the villainous Travis and his Mutoid pilot (exclusively female blood-sucking cyborgs that foreshadowed Star Trek’s Seven of Nine) in charge of the lead ship.

With escape impossible, Blake and co have no choice but to fight, but the battle is soon brought to a halt by a bunch of bare-breasted women on a nearby planet, who intend to show the combatants “the meaning of death”. Blake and Jenna are transported to the planet and ordered to fight Travis and his sexy sidekick to the death. The winners will be allowed to go free, the losers’ ship will be destroyed, etc, etc.

Jenna is soon captured and tied up, and the Mutoid, who is feeling a little peckish, begins eying her up as her next meal. But Travis insists on keeping Jenna alive to act as bait for Blake. Needless to say the plan backfires when the Mutoid is forced to snack on local wildlife and finds it disagrees with her. Blake soon rescues Jenna, has Travis at his mercy, refuses to kill him and impresses the bare-breasted women, etc, etc.

That to the best of my knowledge was the last TV adaptation of Frederic Brown’s tale, and it is to this which I now turn.

Carson (who like most SF heroes of that era doesn’t appear to have a first name) is the pilot of a small one-man scout ship on the outskirts of a huge battle fleet that is about engage a fleet of alien vessels. The aliens, known as the Outsiders have been involved with a number of skirmishes with Earth ships and colonies.

All of a sudden Carson finds himself naked in a small enclosed, circular area. His opponent is a red, tentacled sphere about three foot across, which he refers to as a Roller. A voice informs him that the stakes are rather higher than those that will one day be set for Kirk, Koenig and Blake – should he lose the entire human race will be destroyed. The story then develops into a battle between Carson and the Roller, but there is one major difference between Frederic Brown’s short story and all the TV adaptations it inspired.

At the climax of the story, Carson does kill his opponent.

© Christopher Seddon 2008

Bunsfield Oil Depot Fire

Three years ago today, shortly after six in the morning, the Bunsfield Oil Depot near Hemel Hempstead was rocked by a series of massive explosions which were heard as far away as France and Holland (though I failed to hear them from North London). By the time I heard the news, about three hours later, it was clear that nobody had been killed. I was nevertheless very relieved to make contact with my sister and my nephew, who live just two miles away from the depot. They’d been woken by the blast, but it had done no damage. It was also clear by that time that the explosion was an accident and not a result of a terrorist attack.

During the afternoon I took a number of photographs from Hampstead Heath, from which the smoky cloud from the fire could clearly be seen staining the sky:

I then drove to St Albans, from where a huge plume of smoke was clearly visible:

The soot in the atmosphere resulted in a dramatic, Krakatoa-like sunset.

The M1 was closed to traffic. I took this shot from a bridge over the motorway, about a couple of miles from the depot:

Illuminated by the setting sun, the smoke was rolling directly overhead, producing this almost apocalyptic view:

Another view, from Leverstock Green, about a mile away from the fire. Warning sirens could clearly be heard:

The aftermath. Badly damaged industrial units close to ground zero, as seen on Christmas Day:

© Christopher Seddon 2008