Thursday, 31 January 2013

Do Greater Horseshoe Bats (and their relatives) Menstruate?

Greater Horseshoe bat in Devon Cave

In connection with my interests in human evolution I discovered – thanks to the blog “The Evolving Placenta,” that humans are one of the few mammals which menstruate – and that some bats do. I will, of course, be discussing the evolutionary advantages of menstruation in humans in the talk I am preparing – but I am intrigued by the mention of bats.

The reason for my interest was that in the late 50's I helped with the studies of the Greater Horseshoe Bats carried out in the Buckfastleigh area of Devon by John and Win Hooper. The young are born in communal nurseries between May and July, the earlier dates in mild springs but bats were occasionally observed mating throughout the colder months of the year when they were hibernating in caves – suggesting embryos of different ages might be born at about the same time. Because the bats only have one young a year, at a time when there will be plenty of food, it is important that they don't miss a year's breeding. The prolonged mating season is of interest and I am wondering if evolutionary pressures have caused them to menstruate for the same reason as is suggested for humans. If the womb is prepared at the time of ovulation the fertilized egg finds a ready prepared “bed” where it can get nourishment. It therefore starts growing more rapidly – and if it is defective it can be discarded – and because if the long mating season there is time to prepare another egg (and its ready made bed) in time to mate again. This approach could allow several ovulation, fertilization and mensuration cycles to take place during the lengthy mating season, until there is an acceptable embryo in the womb, in time for the young to be born when the food supply is good.

So why do humans, many other primates, and bats menstrurate? Could it be that if you only have one embryo at a time it is very important to avoid loosing an opportunity to breed. Many other mammals can "solve" the problem of missed pregnancy opportunities by having multiple embryos. 

I wonder if anyone interested in the sexual life of bats can throw any light on whether our U.K. species menstruate?. Due to their conservation status I am sure I would not be welcome to visit the Devon bat haunts to examine females bats to see if they were menstruating!!!

Additional References:

Wednesday, 30 January 2013

How evolution has made us what we are

I have agreed to talk to our local U3A Science & Technology group in February on the mechanics of evolution with a special emphasis on the mechanisms that drive the changes,  and later in the year I may follow up with a talk on human evolution in terms of the fossils, etc, that have been found in recent years.

The following is the "sound byte" summary for the talk together with a list of topics to be considered in drafting the presentation:

How evolution has made us what we are

I examine how recent scientific advances show the ways evolution has shaped the human body and mind – and the important role played by climate change in Africa three million years ago.

Key Topics

  1. The basic elements of Evolution: DNA – Sex – and the mechanisms of gradual change – homology - why our body plan is not that different to the early mammals. (10 minutes)
  2. How tree life shaped the primates – longer childhoods and animal cultures (5 minutes)
  3. Surviving climate change and the African Rain Forests – Living in new environments and the effects on the human body – walking upright – loosing hair – the use of tools - menopause (15 minutes)
  4. An important tipping point – culture and the development of language – we have bigger brains but can we use them more effectively than some other animals? What causes the so-called “God Slot” (20 minutes)
  5. Other Homo species (Neanderthal, Densiovan) and the move out of Africa. The Coming of Civilization – is evolution still happening - are there significant differences between different races and/or the sexes? (10 minutes)

(If you have been following this blog you will know that I am particularly interested in the evolution of intelligence, and how my own research throws some light on possible pathways. While the above talk will mention how the coming of language could lead to a period where, in evolutionary terms, it is more advantageous for human brains to concentrate on rote learning while encouraging imaginative learning (the ability to think for oneself) to become less important. Once the talk is out of the way I will be posting a more detailed argument to show that this is the probable cause of the "God Spot." )

Rural Relaxation: Swans, Ducks and Gulls at College Lake

The snow has gone - and most of the ice covering the marsh at College Lake has melted. These swans has gathered at the edge of the ice sheet to feed, accompanied by a number of pochards, a few tufted ducks, and a host of black-headed gulls.
And I am back online - at least as far as this blog is concerned. I have been continuing my country walks, taking more photographs than I have time to sort out - and I have been working harder than ever on the local history & genealogy side - with more that 50 posts on in January. 

In fact I have been moved to consider posting here on several occasions - about various ways in which we are trapped by the democratic system we have. This ends up electing people whose actions show they are more interested in building a career that depends on short-term sound-byte packaged policies that look good on TV or from the platform of the conference hall. We end up with a government in which rank amateurs (as far as having practical experience how to manage long term changes involving large numbers of people) end up proposing idealistically attractive changes without adequate proper assessment of the alternatives. There is an almost total inability to give proper priority to long term problems such as global warming, where doing nothing till it becomes a crisis is not a vilid solution. If, like me, you are interested in evolution - and how life on this planet evolved - you are automatically worried about what happens next - in the long term as well as the short term - and the future seems gloomy. However I have decided I should not allow depression about the future stop me from speaking out honestly about the present. So expect to hear from me more often in future.