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What follows is loosely based on a workshop I ran at this year's Biolive/ChemEd secondary science teachers' conference. (A most excellent conference, by the way - kudos to those organising & presenting.) I've added a bunch of hotlinked references.

Back when I was in 7th form (or year 13 ie a rather long time ago), the description of human evolution we learned about in bio was essentially a very linear model - and it began with Ramapithecus, dated to around 14 million years ago (mya). Even when I began teaching the subject in secondary school bio classes, the curriculum information still had that linearity: the probable tree went something like Australopithecus africanus → Homo habilis → Homo erectus → Homo sapiens. From memory, the Neandertals were in there as ancestral to our own species, whereas these days they are generally viewed as a sister speciesA

Now, of course, we know that our family tree is much more complex than that, albeit quite heavily pruned in recent geological times, and with a more recent origin for the last common ancestor of hominins and chimpanzees. This knowledge has been informed by both a range of new fossil finds, and ongoing ancient DNA (aDNA) analyses. For example, with the discovery of Homo floresiensis remains (Brown et al, 2004), we had a not-too-distant relative living into our not-so-distant past. And DNA analyses first resulted in the publication of a Neandertal genome (Green et al., 2010), and then in the recognition of interbreeding between Neandertals, sapiens, and another species (the Denisovans), that helped extend our understanding of patterns of migrationB.

Family tree of 4 early human groups

Figure: Family tree of the four groups of early humans living in Eurasia 50,000 years ago and the gene flow between the groups due to interbreeding, From http://news.berkeley.edu/2013/12/18/neanderthal-genome-shows-evidence-of-early-human-interbreeding-inbreeding/  

And the finds keep coming, which makes things difficult for classroom teachers at times. How does it all fit together? How do we accommodate all this in our teaching? [One of the points made by a discussant at the conference was that, while the relevant Achievement Standard talks of 'trends in human evolution', when we look at many of the fossil finds we're seeing a mosaic of features, rather than distinct trends) - but we'll come to that in a minute.]

For example, you might have seen press reports about a fossil ape known as Graecopithecus. Some of the headlines about this really have been rather overblown: "Europe was the birthplace of mankind, not Africa, scientists find", trumpeted the Telegraph in May this year. From that article: 

An international team of researchers say the findings entirely change the beginning of human history and place the last common ancestor of both chimps and humans - the so-called Missing Link - in the Mediterranean region.

Except they didn't. The authors of the actual paper say only that the fossils have "a possible phylogenetic affinity with hominins" (Fuss, Spassov, Begun & Bohme, 2017). But then, that doesn't make such a good headline, does it? Bear in mind, too, that the remains they describe are very fragmentary indeed - a mandible with some permanent teeth, and (possibly) a premolarC - and that they come from two separate geographic locations, Greece and Bulgaria respectively, so the 'reconstruction' that accompanied the story was entirely imaginary. Incidentally, the analysis is new, but the fossils themselves were found quite some time ago - the mandible was unearthed in 1944.

Next up, Homo naledi - those of you who've looked at previous years' scholarship exams will know that this was the focus of a question in last year's paper. This species was first described in 2015, but this year another group of finds were reported by Hawks et al. (2017) that greatly extended our knowledge of its morphology and also its age (Dirks et al. 2017). It turns out that naledi and sapiens may well have been alive during the same time period:

... we have constrained the depositional age of Homo naledi to a period between 236 ka and 335 ka. These age results demonstrate that a morphologically primitive hominin, Homo naledi, survived into the later parts of the Pleistocene in Africa, and indicate a much younger age for the ... fossils than have previously been hypothesised on their morphology.

That is, these fossils show a startling mix of modern and primitive characteristics. As Ian Sample says, in his excellent article in the Guardian (Sample, 2017), 

Homo naledi stood about 150cm tall fully grown and weighed about 45kg. But it is extraordinary for its mixture of ancient and modern features. It has a small brain and curved fingers that are well-adapted for climbing, but the wrists, hands, legs and feet are more like those found on Neandertals or modern humans. If the dating is accurate, Homo naledi may have emerged in Africa about two million years ago but held on to some of its more ancient features even as modern humans evolved.

In yet another paper on the naledi finds, Berger et al. (2017) comment that

It is now evident that a diversity of hominin lineages existed in this region, with some divergent lineages contributing DNA to living humans and at least H.naledi representing a survivor from the earliest stages of diversification within Homo. The existence of a diverse array of hominins in subequatorial [Africa] comports well with our present knowledge of diversity across other savanna-adapted species, as well as with palaeoclimate and palaeoenvironmental data.

In other words, everything we know about species diversity in this particular environment predicts that our lineage should be similarly diverse; it shouldn't be a surprise. By the way, that Guardian article comes with some excellent illustrations, by the way: images of fossils, and diagrams of the cave in which they were found (which is a great story in itself). 

And then another headline: "Oldest Homo sapiens fossil claim rewrites our species' history". I know the headlines attract reader interest, but we see so many like this, and they really are misleading. What this particular paper has done is extend our understanding of the possible duration of our species' existence, but it doesn't 'rewrite' things: it pushes back our origins, and also suggests that early sapiens either ranged much further than scientists had previously thought, or didn't evolve solely in East Africa. These particular fossils were discovered back in the late 20th century, when they were estimated at around 40,000 years old. The much older dates come from analysis of the sediments they're found in.

However, it's worth noting (& is reported in the story at the above link) that not everyone agrees with this analysis. 

Palaeontologist Jeffrey Schwartz, at the University of Pittsburgh, Pennsylvania, says the new finds are important - but he is not convinced that they should be considered H.sapiens. Too many different-looking fossils have been lumped together under the species, he thinks, complicating efforts to interpret new fossils and to come up with scenarios on how, when and where our species emerged. 

"Homo sapiens, despite being so well known, was a species without a past until now," says Maria Martinon-Torres, a palaeoanthropologist at University College London, noting the scarcity of fossils linked to human origins in Africa. But the lack of features that, she says, define our species - such as a prominent chin and forehead - convince htere that the Jebel Irhoud remains should not be considered H.sapiens.

I think there are some great 'teachable moments' here, in incorporating this new information into classroom teaching. The first relates to the nature of science - it isn't fixed, and new data may lead to changes in our understanding. (This both makes science a constant adventure, and also contributes to some public mistrust around science - 'how can we trust those scientists when they keep changing their story?'.) The second is that evolution's not a linear, directional process, and the hominin family tree demonstrates this rather well. And the third is that evolution may result in a mosaic of features, as we see with naledi. 

I'll finish off with a great quote from the discussion thread for a blog post by Steve Novella:

What evolutionary theory predicted was that humans must have evolved from something, and morphologically the great apes are closest to us. So, we should find species that fill in the morphological space between humans and great apes. Further, they should occur in a geological and temporal pattern that makes sense evolutionarily. Finally, when we date the last common ancestor by genetic analysis and fossil analysis, they should roughly fit. 

All of these predictions are true. Evolutionary theory was fantastically successful in that regard - we are finding a whole host of hominid species that are part-way between apes and humans. 

 

A As you might imagine, we had an interesting discussion around what 'species' even means in this context. A rigid application of the biological species concept would preclude neanderthalensis and sapiens being sister species, after all, given the increasing evidence of interbreeding between the two. Of course, further back in the fossil record (beyond the point where useable DNA can be retrieved), we have to rely on morphological characteristics only - an approach that's fraught with difficulties. There's this example in the pachycephalosaur dinosaurs, for example. And the NZ moa - once aDNA techniques made the analysis possible, scientists found that what we thought were something like 22 different species were 11 strongly sexually dimorphic species (large female, small male). 

B From Green et al. (2010): "We show that Neandertals shared more genetic variants with present-day humans in Eurasia than with present-day humans in sub-Saharan Africa, suggesting that gene flow from Neandertals into the ancestors of non-Africans occurred before the divergence of Eurasian groups from each other." 

C As a total aside, back in 1922 there was a flurry of excitement when Henry Fairfield Osborn used a single tooth to posit the existence of "Nebraska Man", supposedly a 10-million-year-old human ancestor, as a means of showing that human evolution was a thing (and that it had happened in the US). He was wrong.  

 

LR Berger, J Hawks, PHGM Dirks, M Elliott, & EM Roberts (2017) Homo naledi and Pleistocene hominin evolution in subequatorial Africa. eLife 6: e24234. DOI: 10.7554/eLife.24234

P Brown, T Sutikna, MJ Morwood, RP Soejone, Jatmiko, E Wayhu Saptomo & Rokus Awe Due (2004) A new small-bodied homin from the Late Pleistocene of Flores, Indonesia. Nature 431: 1055-1061. DOI: 10.1038/nature02999

PHGM Dirks, EM Roberts, H Hilbert-Wolf, JD Kramers, J Hawks, A Dosseto, M Duval, M Elliott, M Evans et al. (2017) The age of Homo naledi and associated sediments in the Rising Star Cave, South Africa. eLife e24231. DOI 10.7554/eLife.24231

J Fuss, N Spassov, DR Begun & M Bohme (2017) Potential hominin affinities of Graecopithecus from the Late Miocene of Europe. PLoS ONE 12(5): e0177127. DOI: 10.1371/journal.pone.0177127

RE Green, J Krause, AW Briggs, T Maricic, U Stenzel, et al. (2010) A draft sequence of the Neandertal Genome. Science 328(5979): 710-722, DOI: 10.1126/science.1188021

J Hawks, M Elliott, P Schmid, SE Churchill, DJ de Ruiter, EM Roberts, H Hilbert-Wolf, HM Garvin, SA Williams et al. (2017) New fossil remains of Homo naledi from the Lesedi Chamber, South Africa. eLife 6: 324232, DOI 10.7554/eLife.24232

I Sample (2017) New haul of Homo naledibones sheds surprising light on human evolution. https://www.theguardian.com/science/2017/may/09/new-haul-of-homo-naledi-bones-sheds-surprising-light-on-human-evolutionThe Guardian

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Chickenpox "parties". They had their day - and that day was before the chickenpox vaccine came on the scene. Because chickenpox can be much worse in teens and adults, back in the day it did make sense to contract the disease in early childhood. In fact, it was almost unavoidable, given the epidemic nature of this virus. But a vaccine is now available, so we've moved on, right? 

Unfortunately, wrong - here's a NewshubZB story on a recent invitation to just such an event. And here's the actual invitation, from the FB page Bring Vaxxed to Australia/New Zealand:

The responses were enthusiastic - and quite frightening. First up, people giving this sort of advice:

They could not be more wrong. Shingles is caused by the same virus that causes chickenpox. It can lie dormant in the peripheral nervous system for years before erupting into a blistering rash that is often excruciatingly & unremittingly painful. The odds of developing shingles, if someone's had chickenpox, are around 1 in 3 for those (like me) in the 'older' demographic, which is why I've had the 'shingles' vaccine (like all vaccines, not 100% effective, but better than nothing). Yes, prior to the varicella vaccine both chickenpox and shingles were effectively unavoidable - but why put a child at such high risk of future pain and discomfort now we have the means to avoid that?

And while we're talking discomfort - the chickenpox blisters can appear internally as well as externally, causing extreme discomfort. But hey, that's transient! And claims to the contrary are clearly fake news.

Chickenpox isn't exactly benign, either. Infants, teens, adults, and those with compromised immune systems (eg due to chemotherapy or immunosupressant drugs) may be more seriously ill and be at high risk of complications. These complications can include bacterial infections, pneumonia, encephalitis, septicaemia, all of which may result in hospitalisation. Despite claims on the "Bring Vaxxed..." page, infection of chickenpox blisters is not exactly rare: between November 2011 & October 2013 144 children were hospitalised with complications of chickenpox. Infections were found in 75% of cases. The median hospital stay was 4 days; 9% of those 144 ended up in intensive care, & up to 20% of cases had ongoing health issues after leaving hospital. Maori & Pacific Island children were overrepresented in these statistics.

This information isn't hard to find. And yet there are people, like those in the images above, who'd prefer to let their children run the risk of outcomes like these instead of use a vaccine with a high chance of conferring immunity (& so preventing shingles in later life). Not only that, they'll happily ask about measles parties (Andrew Wakefield has a lot to answer for, in contributing to the myths around measles vaccination), and even discuss sending swabs from their child to others in Australia. I kid you not.

 

Green nails it.

Are people really so wary of evidence-based medicine that they would rather ask someone they know only through the internet to send a swab of unknown provenance in the mail, in the hope of infecting their own child with goodness knows what?

It appears that some are :(



 

 

 

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Like another, far more significant, blogger, I seem to be spending a bit of time on the subject of vaccines & vaccinations. But - given the mumps outbreaks in Auckland & Waikato, and the measles epidemic in Romania & other countries in Europe - it's a subject worth more than one look. 

As a result of a discussion on a community Facebook page, I discovered that Alfred Russel Wallace had become involved in the antivaccine movement in the UK, & had penned a book presenting stats that appeared to show that smallpox vaccination presented no population benefits. He noted that even after compulsory vaccination was introduced in England, epidemics of this awful disease remained a thing. in his comments on the possible size of the unvaccinated population, he noted that "a large but unknown number of the criminal and nomad population ... escape the vaccination officers". However, a bit more reading shows that there was more to it than this.

It turns out that it wasn't only the 'criminal & nomad' population that avoided compulsory vaccination - avoidance was widespread and it seems that there was no penalty for this. In other words, it should not have been surprising that smallpox morbidity and mortality remained high in the UK after the vaccine was introduced. This excellent article describes both the historical and human consequences of a whole town's refusal to accept vaccination against smallpox: the Board of Guardians of the town of Gloucester had voted in 1887 "to take no futher steps in vaccination prosecutions". The outcome? By 1895 a staggering 83% of the population was not vaccinated.

So when smallpox flared up in the town in 1896 the results were predictable, and horrifying. While the town implemented a mass vaccination scheme in response to the spread of disease, which brought it under control, over the 6-month duration of the epidemic 

1981 people had been infected. Two-thirds of these were children under ten. The handful of these who had been vaccinated all survived. of the unvaccinated, 40% died.

Follow the link. Read the story. Look at the images of Ethel Cromwell, the human face of this particular outbreak. And understand that, if it weren't for vaccination, this disease & its accompanying death and disfiguration would still be with us today.

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In the Spinoff today, there's an OP on the ... 'alternative' ... views of a member of our local City Council. It's worth a read. I knew that the councillor was against the use of community water fluoridation (CWF) as a public health measure, but going by various postings she's made in social media, we can add anti-vaccine to the list. 

For instance: she feels that Council shouldn't pay for its staff to receive the flu vaccine - personally I'd hope that our elected representatives would think about things such as cost-benefit analysis. What are the costs to the organisation of having staff away on sick leave? (The University provides free vaccination against flu because it works out better for the institution that way.) However, her position appears to be based on an argument from incredulity: for some reason she "doesn't trust Ministry of Health recommendations". Personally I'm concerned that someone should choose to oppose public health recommendations via a social media page that identifies them as an elected representative; it can appear to give that opinion more weight.

According to the Spinoff writer, other claims made by the councillor include: that babies given vitamin K may develop childhood leukaemia (wrong); that CWF is linked to ADHD (wrong); that adults with polio can cure themselves by taking vitamin C (wrong) that measles is a hoax (wrong). And - horrifyingly - that whooping cough doesn't kill children (she could not be more wrong, and warning: this is a distressing video to watch). I guess that's what you get when people view Natural News as a reliable source of information.

In that light, I wonder how our councillor views the current measles epidemic in Romania

I'm beginning to think that the very success of vaccination has allowed the rise and spread of antivaccination views. Most people in first-world countries have not had first-hand experience of children dying of measles, diphtheria, and whooping cough; have forgotten the images of wards full of children (& adults) in iron lungs because their muscles are paralysed by polio; are unaware of the >30% mortality rate of smallpox, & the dreadful scarring seen in many survivors. If the promotion of antivaccine views results in communities losing herd immunity, then those diseases - which in many cases are literally only a plane flight away - could come surging back. 
 

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It's a bit concerning to hear of outbreaks of mumps in Auckland & the Waikato, as this suggests that in some areas the number of vaccinated individuals in the population has fallen below what's needed to maintain herd immunity: see Siouxsie Wiles' excellent post on this. One of the admins on my local suburb's Facebook page posted information about the Waikato outbreak, with a reminder to people to check their own & their children's immunisation status. This is because mumps isn't a particularly benign disease, especially in older children, teens, and adults

I suppose we could have predicted that those promoting an 'alternative' take on vaccinations would appear.

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The 'discussion' was mildly entertaining, in that apparently this particular individual's 'brilliant' science education via the University of Google totally trumps all of immunology - especially so when they presented this particular book as evidence that All Vaccines Are Evil. In fact, that totally cracked me up.

Why? Because this book, by Alfred Russel Wallace (yes, that Alfred Russel Wallace) was published in 1889, and was based on data on mortality drawn from the UK's birth and death registers. Unfortunately the admin of our local FB page disabled comments before I could ask just which vaccines were being used way back then, if - as claimed - the book showed that all vaccines were baaaad.

As it happens, just three vaccines were available in the period that Wallace reviewed: smallpox (1797), cholera (1879), and rabies (1885). Given that rabies vaccine was given after exposure to the virus, the only two likely to have been in play in Wallace's England were the vaccines for smallpox & cholera. Wallace seems to have focused on the smallpox vaccine in his book. As you'd expect, conditions for manufacturing, transporting, and using the vaccine were not exactly up to modern standards. According to this article (you'll find the original references cited there),

Until the end of the 19th Century vaccination was done either directly with vaccine produced on the skin of calves or, particularly in England, with vaccine obtained from the calf but then maintained by arm-to-arm transfer; initially in both cases vaccine could be dried on ivory points for short term storage or transport but increasing use was made of glass capillary tubes for this purpose towards the end of the century. During this period there were no adequate methods for assessing the safety of the vaccine and there were instances of contaminated vaccine transmitting infections such as erysipelas, tetanus, septicaemia and tuberculosis. In the case of arm-to-arm transfer there was also the risk of transmitting syphilis.

Nonetheless, childhood vaccination against smallpox was made compulsory in England in 1853 - a measure of the fear with which this disease was regarded. 

During the period surveyed by Wallace, he recorded a 'slight decrease' in smallpox mortality, and there was indeed an epidemic in the final decade of his study. However, he himself notes that the unvaccinated population would have included:

infants dying under vaccination age, ... children too weakly or diseased to be vaccinated, ... [and] a large but unknown number of the criminal and nomad population who escape the vaccination officers. These are often badly fed and live under the most unsanitary conditions; they are, therefore, especially liable to suffer in epidemics of Small-pox...

And given the lack of any other vaccines against measles, diphtheria, typhoid, tetanus and others, it should hardly have been a surprise to his readers (now or then) that deaths from those diseases continued unabated. 

However, I should thank the person who posted that link (although I can't, because she blocked me) - without it, I'd probably never have known about Wallace's stance on vaccinations.

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Blog For Darwin Swan girl - portrait of the author as a young scientist

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