Daily Current Affairs

2000 year old archaeological, botanical and isotopic data in India provide clues to future climate adaptations (GS Paper 3, Environment)

Why in news?

• The site of Vadnagar in semi-arid Gujarat region witnessed mild to intense monsoon precipitation during Historic and Medieval periods respectively and post medieval period (1300-1900 CE) bore a resilient crop economy based on small-grained cereals (millets; C4 plants) reflecting human adaptation in response to a protracted weakening of the summer monsoon, according to a new study.
• The study can help inform strategies to future climate change adaptation to it.

 

ISM in the Indian context:

• Owing to the critical importance of the ISM in the Indian context, its variability in the past and its influence on the early civilizations has not been studied extensively in archaeological context.
• Further, the rarity of Historic sites, systematic excavations, and multi-disciplinary work in the subcontinent, obscure the impact of distinct climate anomalies in the past. 
• The intensity of the ISM precipitation varies over the Indian landmass, due to the variations in latitude, altitude, and distance from the sea.
• Scientists have been tracing historical data on variations of rainfall and its consequences as such studies on changing cropping pattern, vegetation, and cultural development, during last 2000 yrs. provide clues for past human response to climate change and important lessons for modern societies in exploring possible strategies to future climate change.

 

Recent research:

• A team of researchers from Birbal Sahni Institute of Palaeosciences (BSIP), presented a circa (ca) 2500-year human occupation sequence spanning multiple environmental changes at the Vadnagar archaeological site based on archaeological, botanical, and isotopic data.
• The study explores the periods of dynastic transitions and crop harvesting in semi-arid northwest India during past Northern Hemisphere climate events, namely the Roman Warm Period (RWP, 250 BCE-400 CE), Medieval Warm Period (MWP, 800 CE-1300 CE) and Little Ice Age (LIA, 1350 CE-1850 CE).

 

Key observations:

• The data from the site indicate that food production was maintained, even during climate deterioration.
• It was based on archaeobotanical which combines botanical knowledge with the archaeological material. Besides macro botanical remains, micro botanical (phytolith), and isotope and radiocarbon dating of the grains and charcoal were also included in the study. 
• Archaeological settlements have a potential to play a significant role as the region is known to respond to sharp climatic (monsoonal) changes owing to location in the north-western periphery of southwest monsoonal activity in India.
• Further, plants used by ancients provide direct evidence of their choices, activities, and ecological conditions.
• The combined analysis has enabled an assessment for diversification of food crops and resilient socio-economic practices during the past two millennia in the wake of increasing precipitation and period of weakened monsoon (drought) that affected globally.

 

Way Forward:

• The results have implications for studies linking past climate changes and historic period famines, indicating that these were in part driven by institutional factors, rather than climate deterioration alone.

 

Test tube rhinos, why rebuilding doomed species is a desperate race against time

(GS Paper 3, Environment)

Context:

• Recently, the scientists announced the first-ever rhino pregnancy achieved by transferring a lab-made rhino embryo into a surrogate mother.
• It took 13 attempts for the breakthrough with a southern white rhino, a closely-related subspecies that branched away from the northern whites about a million years ago.

Background:

• The death of the last male in 2018 made the extinction of the northern white rhino an inevitability. But already in 2015, a group of 20 scientists from five continents had launched an audacious and expensive project to rebuild the subspecies through in vitro fertilisation (IVF)

• The international consortium of scientists, named BioRescue, is confident that the success can be replicated with 30 embryos of the northern white stored in liquid nitrogen. However, rebuilding a species is easier said than done.

 

Challenges:

• In 2009, four northern white rhinos were brought from a zoo in the Czech Republic to a conservancy in Kenya in the hope that they might breed in their natural environment. The two males have died since, and the two females turned out to be incapable of reproduction for pathological reasons. This meant surrogacy was the only option to produce a northern white calf through IVF.
• Preparing a southern white female, the natural choice for a surrogate mother, is an elaborate process. The first step is to isolate her and put a protocol in place to guard against bacterial infections. The real challenge, though, is to spot when the animal is in oestrus, the fertile window for implanting the embryo.
• This requires the services of a ‘teaser’ a scrubbed and sterilised rhino bull to check when the designated surrogate mother gets interested.
• Mating also triggers an array of hormonal reactions that primes the female for the embryo implant.

 

Issue of genetic viability:

• In this case, since the embryos are all from eggs harvested from two females and sperm taken from a few deceased zoo males, even multiple successes with IVF and surrogacy cannot build a gene pool large enough for a viable northern white population.
• One solution is to broaden the breeding pool by creating sperm and eggs from stem cells extracted from preserved tissue samples stored in zoos. The science has worked in lab mice, but it may not be easily replicable in rhinos.
• Another optimistic argument is based on the natural resilience witnessed in the wild. Rampant hunting had resulted in the southern white rhino population crashing drastically in the 19th century when their numbers had possibly dropped to as low as 20.
• However, due to armed protection and multilateral conservation efforts, the subspecies has made a significant recovery since then, and now number more than 17,000.
• But even favourable outcomes from experiments with stem cell techniques cannot stretch the northern white rhino gene pool beyond 12 animals.
• Crossbreeding the northern and southern subspecies is not a solution since this will result in the loss of certain unique attributes, such as hairier ears and feet, that make the northern white better adapted for swampy habitats.

 

Northern white rhino:

• Breakthroughs in IVF or stem cell technologies can in theory produce northern white rhino calves long after the species is extinct. However, babies are not born genetically hardwired to behave as one of the species. They pick up those traits from family and social interactions.
• So the first batch of IVF northern white calves born to surrogate southern white mothers needs to be raised by northern white adults to learn to be northern whites and carry that legacy for the next batch of IVF calves and, if the species indeed survives, future generations.
• That is why scientists consider it absolutely vital that the first IVF calves are born in time to learn the social and behavioural skills of northern whites from the last two surviving females in Kenya.